Phylogenetic analysis based on the morphology of viviparous freshwater clams of the family Sphaeriidae (Mollusca, Bivalvia, Veneroida)

Abstract

415Korniushin, A. V. & Glaubrecht, M. (2002). Phylogenetic analysis based on the morphology of viviparous freshwater clams of the family Sphaeriidae (Mollusca, Bivalvia, Veneroida).-Zoologica Scripta , 31 , 415 -459. The cosmopolitan viviparous bivalves of the family Sphaeriidae (fingernail clams) comprise not only some of the smallest freshwater molluscs, but also an abundant and ecologically important group that often dominates benthic communities of springs, ponds and swamps. The origin from marine ancestors and their subsequent evolution in limnic environments, in particular the development of distinct reproductive modes including complex parental care repertoires, are largely unresolved. This paper presents the results of a phylogenetic analysis of 69 morphological characters from 57 taxa (54 representing sphaeriids throughout the distribution area plus three outgroups). The heuristic search resulted in 753 most-parsimonious trees of length 154 [consistency index (CI) = 0.682, retention index (RI) = 0.906, rescaled consistency index (RC) = 0.618]. Only Pisidium of the three traditionally regarded constituent genera is supported as a monophyletic group; Sphaerium and Musculium in their traditional deliminations are found to be paraphyletic. Instead, the analysis supports a clade comprising all species of Musculium plus Pisidium as suggested by previous morphology-based classifications. However, the shortest tree alternatively supporting a Sphaerium + Musculium clade suggested by molecular data is only one step longer. Some clades that correspond to the subgeneric divisions of the three traditionally recognized sphaeriid genera are supported. Exclusion is suggested of the taxon Euperidae ( Eupera and Byssodonta , both with ovo-viviparous species) from the true Sphaeriidae that then comprises all species with eu-viviparous reproductive mode, i.e. brooding and nourishing their embryos in specialized brood pouches in the gills. The implications for the reconstruction of the evolutionary history of Sphaeriidae and the availability of existing taxonomic names for the systematization suggested by the present analysis are discussed.

Aspectos morfológicos e de incubação em três espécies de Corbicula Mühlfeld, no lago Guaíba, Rio Grande do Sul, Brasil (Bivalvia, Corbiculidae)

“…Esta grande diversidade de padrões reprodutivos entre Corbiculidae, e especialmente em Corbicula, pode estar relacionada com o amplo espectro ecológico da família (Korniushin & Glaubrecht 2003), principalmente se comparada com Unionoidea e Sphaeriidae que incluem somente formas de água doce e têm uma diversidade reprodutiva mais restrita do que a dos corbiculídeos (Byrne 1998, Mansur & MeierBrook 2000, Korniushin & Glaubrecht 2002.…”

“…Britton & Morton (1979), visando esclarecer esta confusão, apresentaram pela primeira vez diferenças em relação às partes moles para espécimes de Corbicula fluminea (Müller, 1774) e C. fluminalis (Müller, 1774), enfocando principalmente características do sifão exalante e diferenças reprodutivas. A maioria dos trabalhos se refere às características morfológicas de C. fluminea, em decorrência de sua importância e principalmente pelos grandes prejuízos causados na América do Norte, em especial, as questões relacionadas com a captação de água para fins de irrigação, industrial e geração de eletricidade (Britton & Morton 1982, Araújo, Moreno & Ramos 1993, Korniushin & Glaubrecht 2002. Os autores Harada & Nishino (1995) enfocaram aspectos do sifão inalante para diferenciação de espécies japonesas de Corbicula.…”

Revision of the species of Pisidium C. Pfeiffer, 1821 from Argentina, Bolivia, Chile, Peru and Uruguay (Bivalvia, Sphaeriidae

“…Comentarios generales sobre la clasificación subgenérica de las especies sudamericanas del género Pisidium Estudios cladísticos recientes de la familia Sphaeriidae basados en datos moleculares (Cooley & Ó Foighil, 2002, Park & Ó Foighil, 2000Lee & Ó Foighil, 2002) y morfológicos (Dreher-Mansur & Meier-Brook, 2000;Lee, 2001Lee, , 2004Korniushin & Glaubrecht, 2002) y en particular de los Sphaeriinae (Lee & Ó Foighil, 2003) han intentado aclarar las relaciones intragenéricas de Pisidium, a fin de evitar inconsistencias e imprecisiones de propuestas anteriores basadas exclusivamente en caracteres morfológicos (número y desarrollo de branquias, aberturas sifonales del manto, posición del ligamento) (Odhner, 1921;Kuiper, 1962;Heard, 1966). Lee & Ó Foighil (2003) a partir de un análisis filogenético basado en un estudio molecular utilizando secuencias ribosómicas nucleares y mitocondriales, proponen una nueva clasificación genérica y subgenérica de la subfamilia Sphaeriinae.…”

Phylogeny of Sphaerium solidum (Bivalvia) based on karyotype and sequences of 16S and ITS1 rDNA

“…Intrageneric relationships amongst Sphaeriidae are still poorly understood and controversial despite a number of systematic hypotheses proposed based on morphological or molecular data [3,[14][15][16]. Sphaerium solidum was included in the subgenus Cyrenastrum Bourguignat (1854) on the basis of several morphological features: solid shell with clear surface sculpture with concentric ribs, broad hinge with hooked cardinal teeth, separated siphonal retractor scars and open nephridium with elongated dorsal lobe [3].…”

“…Phylogenetic analyses based on a set of morphological characters have revealed monophyly of a group including S. solidum and the species of the traditional Sphaerium s. str. subgenus [3,15]. Karyological features, as well as molecular data, may indicate the evolutionary distance between different taxa that may not be obvious at the morphological level.…”