Local environment and fragmentation by drought and damming shape different components of native and non-native fish beta diversity across pool refuges.

Pool refuges are critical for maintaining stream fish diversity in increasingly intermittent streams. Yet, the patterns and drivers of beta diversity of native and non-native fish in pool refuges remain poorly known. Focusing on Mediterranean streams, we decomposed beta diversity of native and non-native fish into richness difference (RichDiff) and species replacement (Repl), and local (LCBD, LCBDRichDiff and LCBDRepl) and species (SCBD) contributions. We assessed the influence of environmental and spatial factors associated with drought and damming fragmentations on beta diversity components and LCBDs, and of local species richness and occupancy on LCBDs and SCBD, respectively. Overall, non-native species showed a more limited occupancy of pool refuges than native fish. RichDiff dominated beta diversity, though it was influenced by drought and damming fragmentations for native fish and local environment for non-native fish. Repl for native fish was slightly influenced by local environment, but for non-native fish was largely driven by drought and damming, albeit with a contribution of local environment as well. LCBD and LCBDRichDiff increased in pools in low order streams for native fish and at low elevations for non-native fish, and with high or low species richness. SCBD was higher for native species with intermediated pool occupancy, but for non-native species with low occupancy. Our results suggest that stream fragmentation may drive native species loss and non-native species replacement in pool refuges, and that environmental filtering may shape non-native species loss. Pools in lower order streams harbouring unique species-rich or species-poor assemblages should be prioritize for conservation and restoration, respectively, and pools at low elevation with unique non-native assemblages should deserve control efforts. We encourage the partitioning of beta diversity and individual analysis of native and non-native fish in intermittent streams, which may be key in stressing the importance of pool refuges in safeguarding native fish diversity.

Condition and size of the non-native pikeperch Sander lucioperca (Linnaeus, 1758) in Portuguese river basins.

We studied life-history traits focusing on the growth and condition of the pikeperch Sander lucioperca to evaluate its phenotypic plasticity when introduced to new environments. Pikeperch is a non-native fish introduced to Iberian freshwater fauna in 1998 that quickly spread to other river basins through human-mediated activities, occupying now a wide variety of habitats along mainland Portugal. Condition (K and SMI), fork length at age, and length-weight relationships were studied for Portuguese populations. Pikeperch fork length for ages 1, 2, 3, and 4 was different between several populations. We applied generalized linear models (GLM) to study the influence of habitat type, latitude, altitude, time after first detection, and fish prey richness on pikeperch populations size at age 4 and condition. We observed higher condition values on populations from lower altitudes at lentic systems more recently introduced. But higher fork length at age 4 was found in populations from higher altitudes, on older populations with higher prey richness. Habitat type, time since first detection, and fish fauna composition are discussed as the main environmental factors explaining the observed phenotypic plasticity with concerns on predatory impact on native fauna.

Morphometric convergence among European sand gobies in freshwater (Gobiiformes: Gobionellidae).

The five genera of sand gobies inhabit the seas and freshwaters of Europe and western Asia and occupy habitats ranging from fully marine to exclusively freshwater. In this study, we use geometric morphometrics to quantify body shape among sand gobies, in order to investigate how shape has evolved and how it is related to habitat. We also compare body shape between preserved museum specimens and fresh specimens, to determine whether or not fixation and storage in ethanol introduce detectable bias. We confirm that the fixed specimens exhibit significant shape changes as compared to fresh specimens, and so, we perform the bulk of our analyses exclusively on fixed specimens. We find that Economidichthys, Orsinigobius, and Pomatoschistus occupy distinct regions of morphospace. Knipowitschia and Ninnigobius have intermediate forms that overlap with Pomatoschistus and Orsinigobius, but not Economidichthys. This pattern is also in rough accordance with their habitats: Pomatoschistus is fully marine, Economidichthys fully freshwater, and the others fresh with some brackish tolerance. We augment a recent phylogeny of sand gobies with data for P. quagga and interpret morphometric shape change on that tree. We then evaluate convergence in form among disparate lineages of freshwater species by constructing a phylomorphospace and applying pattern-based (convevol) measures of convergence. We find that freshwater taxa occupy a mostly separate region of morphospace from marine taxa and exhibit significant convergence in form. Freshwater taxa are characterized by relatively larger heads and stockier bodies than their marine relatives, potentially due to a common pattern of heterochronic size reduction.

A cytogenetical study on Economidichthys pygmaeus Holly, 1929 (Pisces, Gobiidae), an endemic freshwater goby from Western Greece.

A cytogenetic study was carried out on the chromosomes and the nuclear DNA content of the freshwater goby Economidichthys pygmaeus (Pisces, Gobiidae). The species is characterized by a 2n=46 karyotype consisting of 12 submetacentric and 11 subtelocentric chromosome pairs (NF=70). Major (45S) rDNA genes are terminal-centromeric located on the short arm of a single medium-small sized submetacentric pairas assessed by in situ hybridization, CMA3 staining, and Ag-NOR banding. The haploid (C-value) nuclear DNA content is 0.93±0.003 picograms. The cytogenetical data of Economidichthys pygmaeus were compared with those ones already available for other related gobies.