Zoologische Staatssammlung München, München, Germany.
PLoS One. 2012;7(2):e31314. doi: 10.1371/journal.pone.0031314. Epub 2012 Feb 14.
One clade of Malagasy leaf chameleons, the Brookesia minima group, is known to contain species that rank among the smallest amniotes in the world. We report on a previously unrecognized radiation of these miniaturized lizards comprising four new species described herein.
METHODOLOGY/PRINCIPAL FINDINGS: The newly discovered species appear to be restricted to single, mostly karstic, localities in extreme northern Madagascar: Brookesia confidens sp. n. from Ankarana, B. desperata sp. n. from Forêt d'Ambre, B. micra sp. n. from the islet Nosy Hara, and B. tristis sp. n. from Montagne des Français. Molecular phylogenetic analyses based on one mitochondrial and two nuclear genes of all nominal species in the B. minima group congruently support that the four new species, together with B. tuberculata from Montagne d'Ambre in northern Madagascar, form a strongly supported clade. This suggests that these species have diversified in geographical proximity in this small area. All species of the B. minima group, including the four newly described ones, are characterized by very deep genetic divergences of 18-32% in the ND2 gene and >6% in the 16S rRNA gene. Despite superficial similarities among all species of this group, their status as separate evolutionary lineages is also supported by moderate to strong differences in external morphology, and by clear differences in hemipenis structure.
CONCLUSION/SIGNIFICANCE: The newly discovered dwarf chameleon species represent striking cases of miniaturization and microendemism and suggest the possibility of a range size-body size relationship in Malagasy reptiles. The newly described Brookesia micra reaches a maximum snout-vent length in males of 16 mm, and its total length in both sexes is less than 30 mm, ranking it among the smallest amniote vertebrates in the world. With a distribution limited to a very small islet, this species may represent an extreme case of island dwarfism.
马达加斯加叶变色龙的一个分支，即 Brookesia minima 组，已知包含一些世界上最小的羊膜动物物种。我们报告了这些小型蜥蜴的一个以前未被识别的辐射，包括本文中描述的四个新物种。
方法/主要发现：新发现的物种似乎仅限于马达加斯加北部的单个、主要是喀斯特的地点：Ankarana 的 Brookesia confidens sp. n.、Ambre 森林的 Brookesia desperata sp. n.、Nosy Hara 小岛的 Brookesia micra sp. n. 和 Montagne des Français 的 Brookesia tristis sp. n.。基于 Brookesia minima 组所有指名种的一个线粒体和两个核基因的分子系统发育分析一致支持，这四个新种与来自北部 Montagne d'Ambre 的 Brookesia tuberculata 一起形成一个强烈支持的分支。这表明这些物种在这个小区域内的地理接近度上多样化。Brookesia minima 组的所有物种，包括新描述的四个物种，在 ND2 基因中具有 18-32%的非常深的遗传分歧，在 16S rRNA 基因中具有>6%的差异。尽管这个组的所有物种在外貌上有相似之处，但它们作为独立进化谱系的地位也得到了支持，这是由外部形态上的中度到强烈差异以及明显的半阴茎结构差异所支持的。
结论/意义：新发现的侏儒变色龙物种代表了明显的小型化和微地方性案例，并表明马达加斯加爬行动物中可能存在范围大小-体型关系。新描述的 Brookesia micra 雄性最大鼻口长度达到 16 毫米，雌雄全长均小于 30 毫米，是世界上最小的羊膜动物之一。该物种的分布仅限于一个非常小的岛屿，可能代表了岛屿侏儒化的极端情况。
