DOI: 10.5061/dryad.tg8jg
title: Data from: Morphological vs. molecular delineation of taxa across montane regions in Europe: the case study of Gammarus balcanicus Schäferna, 1922 (Crustacea: Amphipoda)

description: Mountainous areas are characterized by substantial biodiversity and
 endemicity due to their complex geological history and habitat
 fragmentation. Hence, it can be assumed that particularly high species
 richness can be found in organisms with limited dispersal capabilities
 that inhabit mountain streams. A number of scientific papers focus on
 molecular phylogeography or traditional taxonomy of species or species
 groups inhabiting such habitats. However, there is a lack of studies that
 integrate morphological and molecular data to identify and delineate
 cryptic species. For practical reasons, uncovering cryptic diversity is
 crucial in taxa used in biomonitoring. Distinct species, hard to separate
 based on morphology only, may have different tolerance ranges towards a
 variety of factors. Thus, our goal is to combine the two approaches to
 reveal potential patterns of diversification within a species widely
 distributed across European mountains: the amphipod crustacean Gammarus
 balcanicus. The data were obtained from 13 populations spread across the
 range of the species. Individuals were initially ascribed to G. balcanicus
 based on conventional fauna key morpho-anatomical diagnostic features and
 were further analysed for 23 additional features to explore any putative
 diversification. Morphometric data were analysed with use of the multiple
 correspondence analysis and anova. Molecular distances were calculated for
 551-bp-long COI sequences. Test for isolation by distance was performed
 for both morphological and molecular data. The morphometric studies showed
 that some of the analysed features differed significantly between
 populations, although there was only a weak correlation between the
 morphological divergence and the between-population geographical
 distances. Moreover, high morphological diversity was present within
 sites. A set of 42 COI haplotypes was identified among the 135 individuals
 sequenced. No haplotype was shared among populations. The molecular
 p-distances within the nine localities presenting more than one haplotype
 were either almost null (ca. &lt;0.003 for 7 localities) or relatively
 low (ca. 0.01–0.02 for 2 localities). In opposite, the molecular
 p-distances between localities were mostly at a high level (94% of
 pairwise comparisons being &gt;0.14), similar as between other
 well-defined species of the genus Gammarus. Surprisingly, G. balcanicus
 appears to be polyphyletic based on topology of the neighbour-joining
 tree. The level of genetic distance between localities was not correlated
 with their geographical proximity. Globally, combining spatial patterns of
 morphological versus molecular divergence indicates a high level of
 cryptic diversity within a species conventionally defined based upon fauna
 key morphological features. In this context, the name G. balcanicus should
 be applied only to the population from locus typicus, while the other
 populations represent a number of putative distinct species. We may expect
 that such phenomenon would apply also to other animal taxa with conserved
 morphology, which are widespread over different mountain ranges in Europe.
description: raw data
 setRaw data set with used
 for morphological analyses.Raw
 data.xlsx