Polygyrid land snail phylogeny: external sperm exchange, early North American biogeography, iterative shell evolution

Abstract

A fresh assessment of reproductive behaviour and anatomy, combined with new allozyme data, results in a phylogenetic hypothesis for the 23 polygyrid genera that differs substantially from previous attempts. Analyses based on this phylogeny suggest that (a) evolutionary transition from internal to external sperm exchange occurred only once in polygyrids, with unusual functional intermediates still extant; (b) polygyrid biogeographic history paralleled that of plethodontid salamanders, with hypothesized vicariance events at about 145, 120, 65 and 40 MA, and, dispersal events at about 55 and 40 MA; and (c) iterative shell evolution occurred despite a phylogenetic constraint on ontogenetic whorl-expansion rate.

Comparative reproductive biology ofAriolimax californicusandA. dolichophallus(Gastropoda; Stylommiatophora)

“…The pattern found in Ariolzmax of taxa being distinguishable at the species level primarily by characters of the genitalia is common in many taxonomic groups, among them the stylommatophoran gastropods, and Eberhard (1 985) has hypothesized that this rapid evolution of genitalic traits is evidence for sexual selection. The role of sexual selection in the speciation and evolution of the Stylommatophora has become of increasing importance to taxonomists in recent years (e.g., Emberton, 1994;Roth, 1996;Reise, 1996;Jordaens et al, 1998).…”

Mating behaviour in the terrestrial slug Deroceras gorgonium: is extreme morphology associated with extreme behaviour?

“…During copulation, ejaculates are exchanged mutually via everted and more or less entwined penes. External sperm exchange from penis to penis is considered unique to pulmonate gastropods, within which it has evolved at least four times independently (Emberton, 1994). Note that we apply the term 'copulation' exclusively to this phase of sperm exchange, not as a synonym for mating behaviour in general; and by a 'mating' we do not imply that mating behaviour proceeded to completion.…”

Exploratory phylogenetic and biogeographic analyses within three land-snail families in southeastern-most Madagascar

“…E-mail: ken-emberton@mailcity.com Vicariance biogeography requires at least two monophyletic clades for which there are accurate range maps defining discrete, shared areas of endemism, and for which there are robust phylogenetic hypotheses (Kluge, 1988;Griswold, 1991;Emberton, 1994a). A recent symposium volume on Madagascan biogeography (Lourenco, 1996) contained no vicariancebiogeographical analyses (but see Schatz, 1996), perhaps because cladistic hypotheses were rare (Yoder, 1996) or incomplete (Emberton & Rakotomalala, 1996), because island-wide ranges were poorly understood for most groups (many papers in Lourenco, 1996), and because areas of endemism were only starting to be redefined (Raxworthy & Nussbaum, 1996).…”

“…Land snails can be useful for vicariance biogeography because of their ancient origins and their evolutionary and faunal stabilities (Solem, 1979(Solem, , 1981Emberton, 1994a). Land snails can also be practical for conservation assessment because of their restricted distributions and ecological fragilities (Solem, 1984;Kay, 1995;Pearce & Emberton, in press) and because, unlike most other invertebrates, they are identifiable to species at all life stages and for weeks to months after death (Emberton, 1996(Emberton, , 1997Emberton et al, 1999a, b).…”