A multidimensional approach for detecting species patterns in Malagasy vertebrates

Abstract

The biodiversity of Madagascar is extraordinarily distinctive, diverse, and endangered. It is therefore urgent that steps be taken to document, describe, interpret, and protect this exceptional biota. As a collaborative group of field and laboratory biologists, we employ a suite of methodological and analytical tools to investigate the vertebrate portion of Madagascar's fauna. Given that species are the fundamental unit of evolution, where microand macroevolutionary forces converge to generate biological diversity, a thorough understanding of species distribution and abundance is critical for understanding the evolutionary, ecological, and biogeographic forces that have shaped Malagasy vertebrate diversity. We illustrate the means by which we apply Mayr's ''three basic tasks'' of the systematist [Mayr, E. (1942) Systematics and the Origin of Species from the Viewpoint of a Zoologist (Harvard Univ. Press, Cambridge, MA)] to identify, classify, and study the organisms that together constitute Madagascar's vertebrate community. Using field inventory methods, specimen-based studies, and morphological and molecular analyses, we formulate hypotheses of species identity that then serve as the foundation for subsequent studies of biology and history. Our experience, as well as that of other investigators, has shown that much of the vertebrate species diversity in Madagascar is ''cryptic'' for both biological and practical reasons. Beyond issues of cryptic biological diversity, the resolution of species identity in Madagascar has been hampered because of a lack of vouchered comparative material at the population level. Through our activities, we are attempting to remedy these limitations while simultaneously enhancing research capacity in Madagascar.The actual demarcation of species taxa uses morphological, geographical, ecological, behavioral, and molecular information to infer the rank of isolated populations.Ernst Mayr (ref. 1, p.276)

Geographical patterns of deep mitochondrial differentiation in widespread Malagasy reptiles

“…In Madagascan reptiles, the plated lizards of the genus Zonosaurus are an example. Zonosaurus quadrilineatus and Z. trilineatus are closely related and possibly conspecific, and have their respective distributions separated by the Onilahy river in south-western Madagascar (Yoder et al, 2005). For many lemur taxa, the Mangoro river in the Northern Central East is a major dispersal barrier (Goodman and Ganzhorn, 2004).…”

“…Its biodiversity is not only extraordinarily distinctive and diverse, but also endangered, making its exploration an urgent matter. The knowledge of even its vertebrates is far from complete, and new species have been discovered and described at a vigorous pace in the last few years (Yoder et al, 2005).…”

Vast underestimation of Madagascar's biodiversity evidenced by an integrative amphibian inventory

“…Its fauna and flora evolved largely in isolation (23), and many taxa are characterized by a high degree of microendemism within Madagascar (24)(25)(26)(27). The native amphibian fauna is constituted by 5 endemic evolutionary lineages of frogs with 100% species-level endemism, 2 of which (the mantellids and the cophyline and scaphiophrynine microhylids) are very species-rich.…”

A necessarily complex model to explain the biogeography of the amphibians and reptiles of Madagascar

“…Its current vertebrate fauna is a mix of only a few ancient Gondwanan clades and numerous younger radiations, originating from Cenozoic overseas colonizers arriving mainly from Africa [19][20][21] . The extraordinary proportion of family-level endemism in Madagascar, and the long isolation from non-Malagasy sister lineages, provide a unique opportunity to study the mechanisms driving divergence and diversification in situ 22 . Over the past decade, numerous mechanisms and models have been formulated to explain biodiversity distribution patterns and species diversification in Madagascar, pertaining to environmental stability (or instability), solar energy input, geographic vicariance triggered by topographic or habitat complexity, intrinsic traits of organisms or stochastic effects [23][24][25][26][27][28][29][30][31] .…”