Today, my colleagues and I have published a monograph on part of the gecko genus Lygodactylus, describing eight new species from Madagascar in the journal Zootaxa.
Lygodactylus are diurnal geckos, but most species are not as flashy as their cousins, the Phelsuma day geckos. They come mostly in mottled greys and browns. They are universally small geckos, generally not exceeding 10 cm from the snout to the tip of the tail. Yet they have a fascinating biogeographic history: last year, we showed that Lygodactylus have dispersed between Madagascar and mainland Africa three times, and one group even made their way to South America.
The oldest/most divergent group of Lygodactylus are in their own subgenus, Domerguella, and are only found on Madagascar. Until last year, we always assumed that there were just five species of Domerguella: three widespread rainforest species, and two microendemic karst specialists from northern Madagascar. But last year we discovered that there was enormous genetic diversity in this group; the five species were just a small fragment of the total diversity, and there may be as many as seventeen species. Now, we have made a major taxonomic stride forward by describing eight of these lineages as new species, and elevating one subspecies to species rank, bringing us to 14 species of Domerguella.
Part of the reason we didn’t realise there were so many species of Domerguella until now, is that they are all so cryptically coloured, and generally look very similar to one another. Even after painstaking examination, in some cases we could only find very weak morphological features that were useful to differentiate between them. But the enormous genetic differences among them leaves no doubt that these are good species.
Lygodactylus petteri is a species from Montagne d’Ambre that we elevated from subspecies level because of its genetic distinctiveness.
One particularly interesting result was the discovery that there are three or four species on Montagne d’Ambre, a rainforest-clad extinct volcano in northern Madagascar, where there has been intensive previous field work, including the 2017–2018 expedition I led (about which you can read here, here, here, and here). I discovered one of the new species, L. tantsaha, on the west slope of the mountain, where no herpetologist had ever collected before, and we did not find it elsewhere on the mountain, so it may have the habitat to itself. Elsewhere on the mountain, however, the two species L. madagascariensis and L. petteri, as well as a deep genetic lineage that we have not currently described because we do not have enough material to understand it, seem to co-occur. We have not been able to deduce how they co-exist; whether they compete for resources and space, or are somehow ecologically distinct is unknown. Such a density of closely related species in a single location is pretty exceptional!
Remarkably, hardly any of the species that we have described in this paper was thought to represent a new species when the type material was originally collected and deposited in museums. Most were just collected as permanent scientific vouchers proving ‘this species occurs here’. But it was only possible to describe the new species because that collecting work was done. I think this is a critical point: if we only collect animals in the field that we think will probably represent a new species, we are going to be missing a huge number of species that we just aren’t able to tell apart at first (or second) glance. We should continue to take representative samples—carefully, conservatively, and thoughtfully—so that we can ensure we miss as little as possible, and so that we can continue to build the vaults of specimens that serve as the scientific record, even after the habitat they come from is destroyed.
Lygodactylus (Lygodactylus) heterurus is one of the smallest Malagasy geckos, but the newly described L. fritzi is even smaller.
What fascinates me most about Lygodactylus in general is their extremely small size. Domerguella are no exception; the smallest of the new species described is L. fritzi, measuring just 53 mm from snout to tail tip. That makes it the third smallest Lygodactylus (after L. broadleyi and L. roavolana), and one of the top fifty smallest amniote vertebrates. The other species are not much larger. Finding such great and underestimated diversity in a group of tiny vertebrates seems par for the course at this point, after our recent descriptions of so many tiny frogs and chameleons. But each time we discover more such species, it is raising new questions about the anatomy, diversification, and origins of these miniaturised vertebrates. Fortunately, my lab and my collaborators are working to answer some of those questions, so watch this space.
Vences, M., Multzsch, M., Gippner, S., Miralles, A., Crottini, A., Gehring, P.-S., Rakotoarison, A., Ratsoavina, F.M., Glaw, F. & Scherz, M.D. (2022) Integrative revision of the Lygodactylus madagascariensis group reveals an unexpected diversity of little brown geckos in Madagascar’s rainforest. Zootaxa, 5179(1):1–61. DOI: 10.11646/zootaxa.5179.1.1 [pdf]
Dear mr. Scherz, is it possible to obtain a copy of the Lygodactylus article. I don’t get access to the zootaxa base.
Kind regards
René Koller
Hi René, you can get it here: https://www.researchgate.net/publication/363184712_Integrative_revision_of_the_Lygodactylus_madagascariensis_group_reveals_unexpected_diversity_of_little_brown_geckos_in_Madagascar's_rainforest