Pinning down Tenuistemma (Pulmonata: Urocoptidae): local evolution of an extreme shell type

作者：De Weerd Dennis R Uit^*; Velazquez Alejandro Fernandez

来源：Biological Journal of the Linnean Society, 2017, 121(4): 741-752.

DOI：10.1093/biolinnean/blx041

• conchological
• Cuba
• ecological speciation
• endemic
• generic characters
• morphological divergence
• morphospace
• selection
• shell

We report an extraordinary case of local and extreme shell-morphological differentiation within a group of otherwise relatively uniform eastern Cuban land snails. Analyses of multi-copy nuclear (ITS2) and of mitochondrial (COI) DNA sequences congruently place the 'genus' Tenuistemma, occurring monotypically on the Yunque de Baracoa mountain in eastern Cuba, within the more wide-spread species Pleurostemma perplicata from adjacent lower areas. This result is in sharp contrast with patterns of variation in supposedly diagnostic shell-morphological characters, namely (1) differences in both shell form and shell sculpture between Tenuistemma and P. perplicata, (2) the shell-morphological coherence of paraphyletic P. perplicata and (3) the resemblance between P. perplicata and phylogenetically and geographically more distant species placed in Pleurostemma. We conclude that Tenuistemma evolved from P. perplicata on the Yunque de Baracoa, a process that probably started between 0.01 and 1.42 million years ago. The remarkable set of shell features distinguishing Tenuistemma from P. perplicata probably evolved as a result of unique local selection pressures, possibly affecting multiple characters linked in shell development. This study provides a basis for further research into the evolutionary processes behind this remarkable morphological transition. To render the genus Pleurostemma monophyletic, we propose to transfer P. perplicata to the genus Tenuistemma.

• 出版日期2017-8