Effects of habitat transition on the evolutionary patterns of the microgastropod genusPseudamnicola(Mollusca, Hydrobiidae)

Abstract

Delicado, D., Machordom, A., Ramos, M.A. (2015). Effects of habitat transition on the evolutionary patterns of the microgastropod genus Pseudamnicola (Mollusca, Hydrobiidae). -Zoologica Scripta, 44, 403-417. Molecular phylogenies of extant species are considered effective tools to infer mechanisms of speciation. Here, we benefit from this utility to investigate the evolutionary history of an organismal group linked to different aquatic ecosystems, the microgastropod genus Pseudamnicola (family Hydrobiidae). Previous studies have found around 45 species of the nominal subgenus P. (Pseudamnicola), most of them in coastal stream localities of several Mediterranean islands and mainland territories, whereas only 12 species of the other subgenus, P. (Corrosella), have been collected from springs and headwaters of mountainous regions of the Iberian Peninsula and south of France. As springs often act as isolated habitats affecting dispersion and constraining gene flow, we supposed that the temporal history and mode of diversification of species from both subgenera should differ and therefore be reflected in their phylogenetic patterns. To assess this hypothesis, we performed a molecular phylogeny based on mitochondrial and nuclear DNA sequences and later conducted an independent analysis to examine the potential effect of certain geographic and ecological variables in the genetic divergences of the subgenera. Additionally, we estimated the ancestral area of diversification of both groups. Published anatomical revisions and our molecular analyses suggest that the genus Pseudamnicola should be divided into three genera: the two previous subgenera plus a new one described here. As postulated, the evolution of the spring organisms was strongly related to habitat fragmentation and isolation, whereas dispersal followed by divergence seem to have been the most common speciation processes for euryhaline species inhabiting coastal streams and low river stages in which waters remain connected. On the contrary, rather than habitat fragmentation or dispersion, environmental conditions have played a larger role during the deep divergent split leading to the three genera.

Unraveling a new lineage of Hydrobiidae genera (Caenogastropoda: Truncatelloidea) from the Ponto-Caspian region

“…Among the genera contributing most to this remarkable richness is the genus Pseudamnicola Paulucci, 1878 (subfamily Pseudamnicolinae Radoman, 1977). Despite the promotion of its former congeneric subgenus Corrosella Boeters, 1970 to the genus level (see Delicado et al 2015), Pseudamnicola still comprises around 70 nominal species distributed mainly across the western and central Mediterranean region (Glöer et al 2015). However, this richness may be overestimated due to erroneous assignments to the genus since most of its species have been diagnosed according only to a few shell features or at most to both shell and penis descriptions.…”

“…However, Intermaria differs in having smaller shell dimensions (e.g., when compared with the 5 mm height of P. granjaensis Glöer & Zettler, 2007see Delicado et al 2014), a more conic-shaped shell, two basal cusps on the central radular tooth (one in Pseudamnicola), a shorter prostate gland, and a gradually tapering penis with a small distal lobe on the inner edge (penis is triangular with many surface folds and has a blunt end in Pseudamnicola see Delicado et al 2015).…”

“…Although a systematic revision of Pseudamnicola is still pending, Delicado et al (2015) revealed the monophyly of Pseudamnicola s. str. and proposed a series of diagnostic characters including a simple ovate-conic shell shape, single elongated seminal receptacle and broadly triangular penis with several folds across its surface.…”

The genus Mercuria Boeters, 1971 in Morocco: first molecular phylogeny of the genus and description of two new species (Caenogastropoda, Truncatelloidea, Hydrobiidae)

“…Note that genetic distances between Mercuria species are more comparable to those calculated for the genus Pseudamnicola (0.5–10% average 6.7% in Delicado et al 2015), which could be attributed to their similar habitat preferences (i.e., small lowland rivers and streams). This common ecological pattern is suggested by numerous records of these co-occurring genera in Algeria (Glöer et al 2010), Malta (Glöer et al 2015), Spain (Boeters 1988), and Morocco (present study).…”

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“…Based on an integration of morphological, molecular and ecological evidences (Delicado et al, 2015), the freshwater gastropod genus Pseudamnicola has been recently split into three different genera: (1) Pseudamnicola s. str. Paulucci, 1878 with around 60 species distributed throughout much of the Mediterranean islands and peninsulas, (2) Corrosella Boeters, 1970 with 13 known species restricted to the Iberian Peninsula and southern France, and (3) Didacus Delicado, Machordom and Ramos, 2015, a monospecific genus whose unique (type) species, Didacus gasulli (Boeters, 1981), was found at several streams from southeastern Spain and Ibiza island.…”