Allozyme versus discrete morphologic characters in the phylogenetic analysis of the land snailSolatopupa(Pulmonata, Chondrinidae)

Abstract

In the six species of Solatopupa, genetic information apparently disagrees with the taxonomic relationships already inferred from classical comparative analysis of shell morphology; a global reexamination of data in a phylogenetic perspective is therefore required. Different criteria of phylogenetic inference were applied to allozyme data from previous studies (28 loci) and to a matrix of 17 binary factors descriptive of morphological characters (shell and genital anatomy) with the purpose of making a comparative evaluation of the resulting branching patterns. Results show that, in spite of the initial suggestion, there is no inconsistency between genetically and morphologically inferred phylogenies, if the morphological data are thoroughly examined and globally considerd. These data, in fact, are more insidious to interpret and often misleading. In the case under study, the apparent similarity in the shell shape is probably ascribable to homoplasy, and likely to be the result of very different evolutionary processes all leading to a juvenilized (pedomorphic) shell morphology.

Molecular phylogeny and historical biogeography of the land snail genus Solatopupa (Pulmonata) in the peri-Tyrrhenian area

“…Boato (1986) demonstrated an allopatric distribution of populations of S. similis with diVerent chromosome numbers (2N D 60 in populations from Spain to Western Liguria, 2N D 58 in populations from Eastern Liguria to Northern Latium). Subsequently, the same author found more than a 40% of genetic divergence at 28 allozyme loci and slight morphological diVerences between the two chro-mosomal forms (Boato, 1988(Boato, , 1991. On these bases, Eastern populations of S. similis with 2N D 58 were attributed to S. juliana.…”

“…On these bases, Eastern populations of S. similis with 2N D 58 were attributed to S. juliana. In addition, previous phylogenetic hypotheses are available for the whole genus, based on morphology, allozymes, and karyology (Boato, 1986(Boato, , 1988(Boato, , 1991Gittenberger, 1984).…”

“…Should we accept vicariance as the most likely scenario, we will address the timing of the S. guidoni divergence from its continental closest relative. Finally, we want to compare our hypotheses with relationships based on morphology, karyology, and allozymes (Boato, 1986(Boato, , 1988(Boato, , 1991.…”

Useful Characters in Gastropod Phylogeny: Soft Information or Hard Facts

“…In the absence of evidence for that, however, we conclude that all available information should form the basis for the estimation of the evolutionary history. This interpretation is also supported by the incongruence test, which showed that only 5 of the total 28 character matrices yielded signi cant (at the 5% level) length differences between trees from soft and shell characters respectively: Boato (1991), Roth (1991Roth ( , 1996, Jensen (1996b), andWise (1996).…”

“…Ecological and behavioral characters, as well as characters of the radula and operculum, are referred to as "other". Molecular data from Rosenberg (1996) and data on diploid chromosome number from Boato (1991) were also included in the latter category. This category of characters was included in the phylogeny reconstruction to make it as reliable as possible (total evidence, in accord with, e.g., Kluge [1989]), but we have not tested this category against shell and soft-part characters because it is such a heterogeneous assemblage of character types.…”