Population structure, gene flow and evolutionary relationships in four species of the genera Tomocerus and Pogonognathellus (Collembola, Tomoceridae)

Abstract

Genetic diversity and gene flow at 10 allozyme loci were investigated in13 natural populations of four species of the collembolan generaTomocerus and Pogonognathellus. Levels of observed heterozygosity werefound to vary From 0.033 in P. longicornis to 0.120 in T. vulgaris.Average Nei's genetic distances (D) ranged from D = 0.222 betweenpopulations of P. flavescens to D = 0.647 between populations of T.vulgaris. Genetic distances between species were always >1.000 and thehighest value (D = 4.321) was beween P. longicornis and one populationof T. vulgaris. Values of F-ST were very high in all species (from 0.567to 0.696) and levels of gene flow (Nm) derived from F-ST and the privateallele method were low (Nm < 1). Gene flow was significantly higher onlyin two subsets of populations of T. vulgaris. The Plio-Pleistocenicgeological rearrangements and the effect of stochastic events, such asgenetic drift: are invoked to explain the different levels of geneticdivergence between and within species. Distance- and character-basedapproaches were used to reconstruct evolutionary relationships betweenand within species. While the monophyly of ail species was confirmed,the results did not univocally support the monophyly of the two genera,leaving the question of their generic or subgeneric status unresolved.(C) 2000 The Linnean Society of London.