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Crocodiles of New Guinea, crocodiles of the Philippines (crocodiles part IV)

The views expressed are those of the author and are not necessarily those of Scientific American.


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Simplified cladogram of Crocodylus crocodiles showing one possible topology for the clade. Photos (top to bottom) by Mo Hassan, Davric, Herbert Ponting, Dave Hone, Naish, Wilfried Berns. Image of New Guinea crocodile (icon for 'reduced' Indopacific assemblage) licensed under Creative Commons Attribution-Share Alike 2.0 Germany license. For a larger version see the previous article in this series.

ResearchBlogging.org

It’s time to crack on with the Tet Zoo guide to the crocodiles of the world (part I here, part II here, part III here). I haven’t been able to do much on the blog lately due to technical work on pterosaurs, cats and the whole sexual selection project.

Anyway – - in the previous article in this series we looked at the Saltwater crocodile Crocodylus porosus (aka Estuarine crocodile, Indopacific crocodile or Saltie), a species of southern Asia and northern Australasia often considered close to (or part of) an ‘Indopacific assemblage’ of crocodile species. As we saw in that last article, molecular studies indicate that the Saltwater croc is close to the Mugger C. palustris and/or Siamese croc C. siamensis, and maybe not so close to other Australasian species or to the crocodiles of the Philippines. In this article, we look at two of the ‘remaining’ species in the Indopacifc assemblage.

New Guinea crocodile, photo by Wilfried Berns, licensed under Creative Commons Attribution-Share Alike 2.0 Germany license.

Juvenile New Guinea crocodile, photographed at St Augustine Alligator Farm, Florida. Photo by Vladimir Dinets. Interesting in showing how large the hindfeet are.

The New Guinea crocodile C. novaeguineae is a poorly known, medium-sized crocodile species, said to reach a maximum length of 4 m, though 5 m is claimed by some (Wermuth & Fuchs 1978) [portrait above by Wilfried Berns of www.Tierdoku.com; adjacent image by Vlad Dinets, from here]. Its snout is medium in length compared to that of other crocodiles (being about twice as long as it is wide at the base). Distinctive features include longitudinal ridges anterior to each eye and the presence of small, granular scales between the four largest osteoderms on the dorsal surface of the neck. In contrast to the Saltwater crocodile, a transverse row of large cervical scutes is present close to the rear border of the head (Ross & Mayer 1983).

The New Guinea croc was only recognised as a distinct taxonomic entity in 1928. Prior to this, examples were assumed to be immature Saltwater crocs, and even after 1928 doubt remained as to its distinction. It’s mostly a freshwater animal of rivers, lakes and swamps; there are records of individuals from brackish and coastal waters, but it seems that it mostly avoids habitats frequented by the larger and more powerful Saltwater crocodile. Scant data from ecology and diet has led some authors to suggest that the New Guinea and Saltwater crocodiles may avoid competition through niche differentiation, with the former mostly eating fish and birds while the latter takes larger prey (Trutnau & Sommerlad 2006). [Photo below by Midori.]

New Guinea croc, photographed in captivity at Bandung Zoo (Java) by Midori. I'm always interested in the way the 4th and 5th fingers (which generally lack claws) can be oriented strongly 'outwards' relative to digits I-III and often appear quite far 'up' the side of the wrist. Photo licensed under Creative Commons Attribution 3.0 Unported license.

The existence of two morphologically distinct and genetically separate C. novaeguineae populations – one in the north of the island and one in the south – is well known, and people have been saying for decades that this division will eventually result in the naming of distinct subspecies. They differ in patterns of scalation and skull form, with the southern animals having a relatively longer premaxillary region and two or more additional post-occipital scutes when compared to northern ones (Hall 1989). Southern animals also produce smaller egg clutches (on average), have larger hatchlings, and breed in the wet season instead of the dry season (Hall 1989).

It used to be said that the New Guinea crocodile also occurred on the Aru Islands (130 km west of New Guinea), but apparently this is incorrect and based on mistaken accounts of juvenile Saltwater crocodiles. The New Guinea crocodile has, however, been introduced to the Palau Islands in Micronesia (Steel 1989) [UPDATE: nope, this is erroneous. Please see comments].

Crocodiles on the Philippines

Swimming Philippine croc (with another in the background), by Gregg Yan. The obvious presence of postoccipital scutes would allow you to be sure that this isn't a Saltwater crocodile.

A very similar, closely related crocodile often regarded as the sister-species to the New Guinea crocodile (e.g., Meganathan et al. 2010, Man et al. 2011, Oaks 2011) is known from the Philippines. This is the Mindoro crocodile, Philippine crocodile or Philippine freshwater crocodile C. mindorensis, named as a new species in 1935 but later demoted by some authors to the rank of a C. novaeguineae subspecies. In keeping with most recent authors, I regard it as a distinct species.

Intriguingly, Oaks (2011) found C. mindorensis to be paraphyletic with respect to C. novaeguineae: that is, the New Guinea croc was recovered as a population within the Philippine crocodile. This may tell us something about the biogeographic history of these animals. Does this result mean that C. novaeguineae should be sunk into C. mindorensis? Actually, seeing as C. novaeguineae was named first (1928 vs 1935), this is the name that would get used, should the two be combined. The genetic distance between (1) the clade that includes C. mindorensis and the most C. mindorensis-like specimens of C. novaeguineae, and (2) the remainder of C. novaeguineae was still relatively great, suggesting a separation that occurred somewhere between 6.8 and 2.6 million years ago. Separate species status for these crocodiles should therefore be maintained (Oaks 2011)… though, as usual, we run into the usual problem of deciding just what a ‘species’ really is. Oaks (2011) even suggested that some crocodile populations on New Guinea should best be interpreted as C. mindorensis, meaning that both species occur on the island.

Anyway, the Philippine crocodile (as conventionally understood) is relatively small, mostly 1.5-2 m long in total but with some individuals perhaps reaching 3.5 m. Its dorsal osteoderm shield is more complete than that of C. novaeguineae, and the four large scutes of the cervical shield aren’t separated by small scales as they generally are in C. novaeguineae (Ross & Mayer 1983). It also has a proportionally shorter snout than C. novaeguineae and the top of its head is more distinctly textured, often giving individuals a more ‘gnarly’ look. It tends to be white ventrally and dull brown dorsally, often with transverse stripes.

Philippine crocodile, photographed on Palawan by Gregg Yan. Licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

Until very recently, the Philippine crocodile was present across most of the Philippine islands from north to south. It must have been extremely abundant as late as the 1930s, since in 1932 a single American hunter apparently killed over 12,000 individuals for their leather in a single six-month period (Trutnau & Sommerlad 2006). Due to this level of hunting, it seems to have disappeared from most islands and today remains present in small numbers on Luzon and Mindanao alone. The populations on Mindoro and Negros apparent became extinct in the 1990s. Its former presence in the Sulu archipelago (just to the west of Mindanao in the southern part of the Philippines) has been mentioned (Steel 1989).

Dorsal osteoderm compliment of C. novaeguineae (left) and C. mindorensis (right), from Ross & Mayer (1983). In C. novaeguineae the large cervical scutes tend to be separated by granular skin and there is a band of skin posterior to the cervical shield; in C. mindorensis, there is usually one or two scutes immediately posterior to the cervical shield and the anterior-most scute rows in its dorsal shield tend to be more 'complete'.

In fact, persecution of this species has been so severe that only about 100 post-hatching individuals were thought to be present in the late 1990s, making it critically endangered. Captive breeding efforts during, and since, the 1990s resulted in the hatching of over 1000 babies, though problems of funding and disease transmission have meant that these conservation efforts were not quite the success story they should have been. Furthermore, reintroduction projects were hampered by uncertainty over the affinities of the animals concerned, since some individual acquired from private collections were suspected (and confirmed) of being C. mindorensis x C. porosus hybrids. In a 2010 PhD project devoted to this issue (Hinlo 2010), Ma. Rheyda Penetrante Hinlo was able to distinguish hybrid Philippine crocs from pure ones – unfortunately, some of the hybrids had already been released as part of a 2009 reintroduction effort (Hinlo suggested that these individuals should be captured and removed from the breeding population). On top of these problems, crocodiles on the Philippines still have an image problem, with many locals viewing them negatively and as a danger to livestock and people.

The surviving northern and southern C. mindorens populations are genetically distinct (about as distinct as are mainland and Madagascan populations of C. niloticus), but it probably isn’t advantageous to view them as separate populations when it comes to management (Hinlo 2010).

With the New Guinea and Philippine crocodile done, we’re left with a single member of the traditional Indopacific assemblage: the Australian Johnston’s crocodile, Freshwater crocodile or Freshie. That’s the species we’ll be looking at next.

For previous Tet Zoo articles on crocodiles, see…

Refs – -

Hall, P. 1989. Variation in geographic isolates of the New Guinea crocodile (Crocodylus novaeguinae Schmidt) compared with the similar, allopatric Philippine crocodile (C. mindorensis Schmidt). Copeia 1989, 71-80.

Hinlo, Ma. Rheyda Penetrante 2010. Population Genetics and Conservation of the Philippine Crocodile. Unpublished MSc thesis, Massey University, Manawatu, New Zealand.

Man, Z., Yishu, W., Peng, Y. & Wu, X. 2011. Crocodilian phylogeny inferred from twelve mitochondrial protein-coding genes, with new complete mitochondrial genomic sequences for Crocodylus acutus and Crocodylus novaeguineae. Molecular Phylogenetic and Evolution 60, 62-67.

Meganathan, P. R., Dubey, B., Batzer, M. A., Ray, D. A. & Haque, I. 2010. Molecular phylogenetic analyses of genus Crocodylus (Eusuchia, Crocodylia, Crocodylidae) and the taxonomic position of Crocodylus porosus. Molecular Phylogenetics and Evolution 57, 393-402.

Oaks JR (2011). A time-calibrated species tree of Crocodylia reveals a recent radiation of the true crocodiles. Evolution; international journal of organic evolution, 65 (11), 3285-97 PMID: 22023592

Ross, F. D. & Mayer, G. C. 1983. On the dorsal armor of the Crocodilia. In Rhodin, A. G. J. & Miyata, K. (eds) Advances in Herpetology and Evolutionary Biology. Museum of Comparative Zoology (Cambridge, Mass.), pp. 306-331.

Steel, R. 1989. Crocodiles. Christopher Helm, London.

Trutnau, L. & Sommerlad, R. 2006. Crocodilians: Their Natural History and Captive Husbandry. Edition Chimaira, Frankfurt.

Wermuth, H. & Fuchs, K. 1978. Bestmmen von krokodilen und ihrer Häute. New York, Gustav Fischer.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Hai~Ren 9:49 pm 06/24/2012

    I wonder how the supposed paraphyly of C. mindorensis works out; is it based on geography, say, crocodiles on certain Philippine islands being more closely related to C. novaeguineae?

    I’m particularly intrigued by the apparent niche-partitioning between C. porosus and the various freshwater Indo-Pacific species; we know that C. porosus does inhabit freshwater habitats, so I wonder if there’s competitive exclusion or sympatry, and if intra-guild predation is common.

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  2. 2. Hai~Ren 10:09 pm 06/24/2012

    Just skimmed through Oaks, 2011 (accessible here), and also managed to access the supporting information. Only 2 samples of C. novaeguineae were included, both from captives (no info on where these captives originated); out of the 7 samples of C. mindorensis, 6 came from Mindanao, with 1 from Busuanga in the Calamian group of islands between Mindoro and Palawan. So perhaps we need more samples of both species from wild-caught individuals, and hopefully from individuals that are clearly not misidentified, or hybrids with C. porosus.

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  3. 3. vdinets 12:27 am 06/25/2012

    Hai~Ren: good questions. There is definitely some habitat overlap between the two saltwater spp. and the more localized freshwater ones; it was probably even more extensive before humans caused habitat and population fragmentation. Many (if not all) species of Crocodylus can hybridize in captivity, and at least some do so in the wild. What mechanisms maintain species distinctiveness, and why do they break down sometimes (as seems to be the case with American and Cuban crocs) is not known. I hoped that my signaling study would provide some answers, but it didn’t. It looks like the difference in breeding seasons might keep them apart a bit, but that’s just a guess. The case of broadly sympatric Nile and Sacred crocs is even more mysterious.

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  4. 4. Dartian 12:46 am 06/25/2012

    Darren:
    The New Guinea crocodile has, however, been introduced to the Palau Islands in Micronesia

    On purpose? For what reason?

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  5. 5. Hai~Ren 2:06 am 06/25/2012

    Says (here) that “The report of a small introduced C. mindorensis population on Palau is known to be in error (Messel and King 1992a).”

    I also found this interesting article from the 1993 Regional Proceedings (Eastern Asia, Oceania, Australasia) of the IUCN’s Crocodile Specialist Group, which looked at crocodiles in the Solomon Islands, Vanuatu, and Palau. Says that only C. porosus is present on Palau…

    Wataru Kimura (1968) reported finding three species of crocodile in Palau during his trip to the islands in 1967, the Philippine crocodile, Crocodylus mindorensis, and the New Guinea crocodile, Crocodylus novaeguineae, in addition to Crocodylus porosus.

    [snip: The article discusses provenance of crocodiles imported to stock a crocodile farm on Palau before World War II, which includes imports from the Philippines and New Guinea]

    Kimura (1968) did not explain how he distinguished between C. porosus, C. mindorensis and C. novaeguineae, but apparently it did not involve the morphological characters used by most crocodile biologists, the presence in mindorensis and novaeguineae of four enlarged, bilaterally symmetrical (i.e. two on each side of the midline) postoccipital scutes on the nape between the skull and the enlarged nuchal cluster, and their absence in porosus. Possibly Kimura recognized different forms based on skin colour as in February 1969, he wrote to Robert Owen, a biologist for the US Department of the Interior, Office of Territorial and International Affairs, Trust Territories Administration, seeking replacements for “New Guinea black skin crocodiles” from Palau that had died. Possibly he mistakenly believed that the occasional C. porosus with one slightly enlarged postoccipital scale on one side of the neck was C. novaeguineae or C. mindorensis.

    Kimura (1968) reported that Crocodylus novaeguineae was found in the east coast rivers of Babeldaob, while Crocodylus porosus and Crocodylus mindorensis, and a few Crocodylus novaeguineae, occurred in the west coast rivers. We found only C. porosus in Palau’s rivers, estuaries, and in the freshwater Ngerdok Lake. We also examined every captive crocodile that we could in Palau and two specimens in the Balau National Museum; without exception they are all C. porosus.

    More recently several popular publications (e.g. Thyssen 1988) have suggested that two species of crocodiles, Crocodylus porosus and C. novaeguineae, are found in Palau and that a third form, a hybrid between the two, now is widespread through the islands. There is no evidence that C. novaeguineae ever occured in Palau and there is no evidence of any hybrid on the islands. Until evidence to the contrary is produced we will continue to believe that Crocodylus porosus is the only species of crocodile that occurs in Palau.

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  6. 6. naishd 4:18 am 06/25/2012

    Thanks for great comments. On the sample size of C. mindorensis and C. novaeguineae specimens used in Oaks (2011) (comment 2), I did mean to say that it was very small. Indeed, Oaks himself said “However, both samples of C. novaeguineae used in this study are from captive animals, so the results should be treated with caution” (p. 3291).

    Darren

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  7. 7. naishd 4:23 am 06/25/2012

    And, ok, so now we know that C. mindorensis does not occur on Palau after all – thanks loads, Hai~Ren, for sorting that out. This shows what sometimes happens when you follow what they say in ‘review’-type books. As per the quotes above, my answer to Dartian’s question (comment 4) would have been that the animals were most likely introduced for farming/exploitation – the result of some enterprising project whereby crocs were going to be bred for their skin and/or meat. People have seemingly moved (small) crocodiles around quite a bit for this reason – something we should keep in mind when considering the presence of certain species in unexpected places.

    Darren

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  8. 8. Heteromeles 2:34 pm 06/25/2012

    I’d also add that the crocs sound quite a bit like oaks. For non-botanists, oaks have three subgenera (possibly four–I’m doing this from memory as quick example. There are three subgenera where I live). They hybridize readily within subgenera, but not across subgenera. The thing about oaks is that they tend to be long-lived generalists within certain habitats, and they tend to be wind pollinated. They therefore display substantial hybridization, especially among genetic markers, and in some cases, populations cannot be readily identified to species. Still, all oak species are identifiable, at least at most places within their distributions.

    From what I’m reading here, crocs seem to work the same way. I’d therefore suggest that a certain degree of skepticism about species assignments is always warranted, particularly when looking at genetic markers, when studying specimens from unusual habitats, and in areas where all the remaining crocodiles are piled together due to nearby development.

    The basic point is that oaks have maintained this counter-intuitive breeding system for millions of years, and they’re doing just fine. It’s entirely possible for species with porous breeding boundaries to do extremely well, while simultaneously maintaining some semblance of separate species within the clade.

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  9. 9. naishd 4:15 pm 06/25/2012

    Loathe as I am to go too far with the oak analogy (smiley)… there are now several cases where crocodile populations have been identified to species level on the basis of overall anatomy, only for genetics to show that their apparent ‘true’ affinities lie elsewhere (best example: Cuban populations of the American crocodile C. acutus look like C. acutus from Central America, but group with Cuban crocs C. rhombifer in terms of genetic closeness). It may well be partly or mostly due to rampant hybridisation that has resulting in confusing introgressive ‘mosaics’ – but one good question is: how ‘natural’ is it? That is, is this hybridisation occurring more than it did in the past because reduced populations, restricted to shrinking habitats, are coming into regular contact with congeneric close relatives more than they did in the past? A familiar theme in the modern world…

    Darren

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  10. 10. mshirley 4:33 pm 06/25/2012

    Hey all. I just wanted to chime in on the New Guinea crocs used in the Oaks study. Both animals were of captive origin and housed at the St. Augustine Alligator Farm. The SAAF has always regarded the individual that clustered with mindorensis as a northern novaguineae and the others as southern. In fact, I think that they know the specific origin of the crocodiles and it is very likely this is accurate. It is also unlikely that they are the results of hybridization in captivity. So, assuming that this is true it certainly creates an interesting scenario where by mindorensis (or northern novaguineae) is codistributed between the two islands (Philippines and New Guinea) and the southern populations may warrant species/subspecies designation. The biogeography here is a bit out of my depth, but as I understand it this scenario may actually make sense in terms of how the island New Guinea was formed.

    I agree that further research involving many more specimens from each putative area (Philippines, north and south New Guinea) is needed, but if we can have any confidence in the supposed origin of the samples used in Oaks then it really suggests something very interesting is going on here! I look forward to the day someone finally gets on top of this…

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  11. 11. naishd 4:37 pm 06/25/2012

    Matthew (comment 10): wow, that’s great, thanks. How do you know this?

    Darren

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  12. 12. mshirley 4:48 pm 06/25/2012

    Hi Darren… I work pretty closely with the SAAF and they support a lot of my work. For example, the captive specimens that we used for the C. niloticus vs. C. suchus karyotyping in the 2011 Hekkala et al. paper came from the SAAF. So, when the Oaks paper came out I asked them about the specimens. Easy!

    Unfortunately that purported northern specimen died. There is still blood from him floating around (actually, its sitting on a shelf not 2m behind me as I type). We’re trying to figure the best next moves with it. There are two very large, genome level projects going on at the moment (one headed by Rob Meredith, George Amato and John Gatesy, the other by Travis Glenn, David Ray, et al.) who should make use of it. But really what needs to happen is one of those Aussie labs needs to put a hold on some porosus work and get up to PNG, sample the crap out of novaguineae and work this issue out. Actually, it would really just require a visit to the Mainland Holdings facility and sample hatchlings, as far as I know they keep their ranched individuals from the north and south separated. So it should be super easy. We’ll see!

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  13. 13. Dartian 1:42 am 06/26/2012

    Darren:
    It may well be partly or mostly due to rampant hybridisation

    Hm, could we have a list of all the crocodile species – or even crocodilian species in general – that are known to hybridise with each other (either in the wild or in captivity)?

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  14. 14. Jerzy v. 3.0. 7:22 am 06/26/2012

    Just two ponderings. One is wondering whether hybridization between crocodilians is really recent event?

    Second is, how well are croc species defined in the first place and how much individual variability exists?

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  15. 15. vdinets 9:59 am 06/26/2012

    Jerzy: (1) no, it is not, at least in some cases. There is evidence of ancient hybridization between Cuban and American crocs in Florida. (2) Most of them are really well-defined phenotypically: you can teach a 3-year old kid to easily ID all New World species… but sometimes you get weird things, like American crocs that look like Morelet’s (there is one in the zoo in Tuxtla Gutierrez, Chiapas).

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  16. 16. naishd 11:05 am 06/26/2012

    I knew that any mention of hybridisation would result in the inevitable “So – are they really distinct species?” question (smiley). I absolutely agreed with Vlad (comment 15). As mentioned throughout this series, this is a bit of intraspecific variation within recognised crocodile species (in, for example, snout proportions, the size of the squamosal crests, the presence/absence of certain transverse scute rows), but – even with this variation taken into account – the populations do otherwise, generally, fall into distinct sets (= species) that you can recognise when you know what to look for.

    As I’ve said before, the existence of hybridisation within a group isn’t a red flag for the validity of a species – rather, hybridisation is natural, occurring opportunistically should behaviour, morphology and genetics allow it. And reduced populations, restricted to smaller areas of habitat, may be hybridising more now than they were in the past.

    Darren

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  17. 17. mshirley 12:42 pm 06/26/2012

    This discussion of what does hybridization mean for defining crocodile species really highlights one of the key conflicts in the crocodile community currently – and that is that we really don’t have a very operational definition or working concept of the species unit. So far it seems we have been quite contented to identify aggregates of morphologically similar entities that are geographically codistributed in some logical way.

    However, with the volume of genetic research showing significant evolutionary heterogeneity in the African crocodiles or homogeneity as may be the case with intermedius and acutus, for example, there is lots of confusion regarding what we’re dealing with. We are way past time in sitting down and really defining our operational species units and what makes them such, and unfortunately we are starting to see that this is having significant ramifications on conservation and management strategies, international legislation, funding availability, etc…

    I fully agree that hybridization is not a red flag for species validity, otherwise we’d have to collapse the entire genus Crocodylus into a single species based on what we know is happening in the wild or will happen in captivity given the opportunity. How then do we conceptualize crocodile species – smallest, inclusive, phylogenetically monophyletic aggregates? Morphological similarity? Maybe its obvious that I favor the former, or some variation of it… but its certainly an interesting discussion!

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  18. 18. naishd 12:53 pm 06/26/2012

    Shame there’s no “like” function in the comments here. Chris Brochu said a similar thing on facebook recently (about the need for a better handle on how many OTUs there are in Crocodylus). Given that there is both (1) a sensible more-or-less consensus/tradition regarding which populations need to be named as species, and (2) given that said populations can (mostly) be justified on the basis of morphology, range and genetics, it surely wouldn’t be too difficult to iron things out for the majority of taxa… it’s those grey areas where sensible decisions are needed.

    But, yes, seems high time that a future crocodile worker’s meeting should have a roundtable session or such where the OTU issue is thrashed out.

    Darren

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  19. 19. Morgan Churchill 5:13 pm 06/26/2012

    Crocodiles are not the only group completely neglected as far as defining OTU’s marine mammals are if anything even worse, and suffer the same hybridization problems as in crocodiles

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  20. 20. Morgan Churchill 5:16 pm 06/26/2012

    also: edit fail on the above

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  21. 21. naishd 5:45 pm 06/26/2012

    Morgan, yes – rampant hybridisation, not only across ‘genera’, but even across ‘subfamilies’ in both pinnipeds (e.g., arctocephalines and otariines) and odontocetes (e.g., orcinines and delphinines). And, yes, I know full well that those ‘subfamilies’ are artificial and non-monophyletic…

    Darren

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  22. 22. Heteromeles 7:49 pm 06/26/2012

    I’m vastly cheered by the discussion above. It’s nice to see non-botanists scratching their heads about OTUs.

    As for “sensible decisions”…good luck with that. My informal guess is that crocodilians (sensu maximo lato) have hybridized since the Jurassic if not the Triassic, and that’s where the modern species (mostly) came from. I say mostly because I’m sure some croc population somewhere hasn’t been engaging in interspecies sex for the last few million years, just because panmixis never universal.

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  23. 23. vdinets 10:21 pm 06/26/2012

    Dartian: I’m not aware of any hybridization between any crocodilians other than various Crocodylus species as well as yacare and spectacled caimans, which interbreed in captivity. Of course, the contact zone of the two parapatric Osteolaemus has never been checked for that (one thing I’d love to do if I had a chance). Also, it’s totally possible that I’ve missed something.

    Darren: the problem with agreeing on a standardized croc taxonomy is that at least two critically important pieces of the puzzle are missing: the status of Philippine/NG taxa and the details of the Nile/Sacred relationships and their subspecific systematics. For everything else it seems more a problem of definitions that missing data.

    BTW, has anyone heard of New and Old world crocs hybridizing in captivity?

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  24. 24. Wilbert Friesen 4:48 am 06/27/2012

    I wonder about the length of the Phillipines croc. Not so long ago the Philippines were inhabited by much larger prey, such as dwarf buffalo’s and the isles must have been absolutely chocked with wild pigs and deer which can reach oncredible densities when left alone. Couldn’t the Phillipine croc be much bigger in those ‘Eden’ days ?
    I find it strange that the New Guinean croc -which could only feed on kangaroos, possum and rats would be bigger than the Philippine one. Of course there where probably some diprotodontids and short-faced kangaroos around at the time but I thought they (esp. the diprotodontids) were more the creatures of the highlands and mountains and if so mostly out of reach of the crocs.

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  25. 25. Heteromeles 12:33 pm 06/27/2012

    I’d say it’s worth getting curious about New Guinea rivers. To me, it’s strange that rivers that are pretty large have such depauperate fish fauna. Perhaps they were fished out hundreds to thousands of years ago?

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  26. 26. Jerzy v. 3.0. 5:55 am 06/28/2012

    I agree with Darren, local hybridization and evidence of a past introgression is common among existing species.

    Also, genetics should not trump morphology and ecology in taxonomy and conservation. For conservation, preserving keystone species with unique ecological niche is more important than preserving genetic variants without any practical use in molecular biology.

    Nevertheless, it would be good to double check the variation of crocodilians especially Philippine-New Guinean. It is a fact that populations of well known species can be misassigned taxonomically in plain sight.

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  27. 27. Jerzy v. 3.0. 5:58 am 06/28/2012

    @vdinets
    What Cuban crocs were doing in Florida?

    I think New World and Old World crocs hybridized in captivity. From memory – Cuban somewhere in croc farms in SE Asia?

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  28. 28. naishd 6:03 am 06/28/2012

    I thought the evidence of Cuban x American croc hybridisation comes from Cuba… it’s something I’ve written about for a later part in the series.

    Re: Jerzy’s mention of possible Cuban croc hybridisation in SE Asia… this species is definitely kept and bred in some Thai croc farms, so it’s certainly plausible.

    Darren

    Link to this
  29. 29. vdinets 12:51 pm 06/29/2012

    Cuban and American crocs hybridize in Cuba now; there is also evidence of past hybridization in the Florida population of American crocs. Cuba, Florida and the Bahamas used to be connected or almost connected. There are fossil Cuban crocs from the Bahamas, and apparently they used to occur in Florida as well.
    Sorry, I can’t provide citations at the moment – crappy internet.

    Link to this
  30. 30. Morgan Churchill 6:22 pm 06/29/2012

    Given overall distances it doesn’t surprise me that recurrent invasions of crocs of both species would have occurred in Florida. I believe there is genetic evidence for this for Manatees, who were wiped out during every glacial maximum, only to invade Florida when temperatures were warm enough to do so. Crocs seem to have similar sensitivities to cold weather.

    Link to this

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