Uwe Römer

Habitat selection and population trends in terrestrial bird species of Robinson Crusoe Island: habitat generalists versus forest specialists

Habitat loss and degradation on oceanic islands are key processes leading to population decline of endemic birds and facilitating the establishment of invasive bird species. In this study, carried out in the Robinson Crusoe Island, we assessed density and habitat selection of terrestrial bird species, including juan fernandez firecrown and juan fernandez tit-tyrant, two endemics, as well as green-backed firecrown and austral thrush, which apparently originate from the mainland. Results show that perturbed habitats contained a low density of the endemic species whereas the mainland species were significantly more abundant in perturbed scrub habitats. Bird species show different habitat selection patterns, with endemics selecting for native forest and mainland species selecting for perturbed habitats, or using them at random. Bird species experienced temporal trends in their overall population sizes, with the endemic tit-tyrant suffering a significant decline in its population size of about 63% between 1994 and 2009. Only mainland species exhibited temporal changes in habitat use, significantly reducing their densities in the preferred scrub habitats, possibly as a response to decreased habitat quality. Thrushes apparently were able to compensate the population decrease in one non native habitat type by using native forests, a habitat giving them the opportunity of preying on nests of endemic species. We conclude that endemic bird species behave as specialists whereas the mainland species must be treated as invasive generalists on Robinson Crusoe Island.

Molecular identification of a cryptic species in the Amazonian predatory catfish genus Pseudoplatystoma (Bleeker, 1962) from Peru

AbstractPseudoplatystoma species are highly prized South American Pimelodid migratory catfishes. Until recently, their taxonomy was not clearly established, with discrepancies between morphological and molecular analyses. Here, Pseudoplatystoma species from the Peruvian Amazon were characterized at the molecular level from a sample representing the observed range of their color pattern variations in the study area. Analyses were performed using seven microsatellite loci for 103 specimens and, for part of them (52), using sequences of two regions of their mitochondrial genome [Cytochrome Oxidase subunit I (COI) and Control Region (CR)]. Factorial correspondence analysis and assignment tests based on microsatellite polymorphism showed that the specimens originally identified as P. punctifer belonged to two different gene pools highly differentiated from P. tigrinum. Morphological examination identified two different morphotypes (with and without black stripes), suggesting the existence of two distinct taxa within P. punctifer. This result was corroborated by the ML tree based on CR sequences, where all individuals but four clustered in a similar way as in the FCA and Bayesian assignment tests. For these four individuals, mitochondrial introgression or retention of ancestral polymorphism was likely. In contrast, the ML tree based on COI sequences showed that reciprocal monophyly was not yet achieved for this marker for the two P. punctifer taxa. The existence of three sympatric species of Pseudoplatystoma in the Peruvian Amazon is discussed in relation to their molecular characteristics, color patterns and ecology. Evolutionary scenarios regarding their divergence are hypothesized.

Importance of nest attributes in the conservation of endemic birds of the Juan Fernández Archipelago, Chile.

Summary Understanding the particular nesting ecology of island endemic species represents the first step in identifying suitable micro-habitats and establishing efficient management programmes. This could become even more important when island bird assemblages are prone to invasion by ecologically similar species that may eventually cause niche compression or the extirpation of species already present on the island. In this study we describe the nesting ecology of both native and introduced landbird species of the Juan Fernandez Islands and determine the extent to which native species could be negatively affected by alien competitors. A total of 119 nests belonging to the 11 resident landbird species were analysed. Landbirds exhibited a wide range of nesting habitat preferences on the different islands, covering different vegetation types, altitudes and ecosystems. By means of a cluster analysis we determined that competition between alien and endemic species apparently does not represent an important factor affecting resource use by endemic birds. Endemic landbirds preferred sites comparatively higher above the ground, with a greater slope and a larger level of shelter, than alien species. The introduced hummingbird, the Green-backed Firecrown Sephanoides sephaniodes, had different nesting preferences to the endemic Juan Fernandez Firecrown S. fernandensis, whereas the House Sparrow Passer domesticus selected nest sites located in populated areas, suggesting that both alien species may not be competing with endemic passerines for nest sites. However, urgent measures are necessary to reduce the potential predation risk on Juan Fernandez Firecrown nests by the alien Austral Thrush Turdus falcklandii.

Tempo and rates of diversification in the South American cichlid genus Apistogramma (Teleostei: Perciformes: Cichlidae)

Evaluating biodiversity and understanding the processes involved in diversification are noticeable conservation issues in fishes subject to large, sometimes illegal, ornamental trade purposes. Here, the diversity and evolutionary history of the Neotropical dwarf cichlid genus Apistogramma from several South American countries are investigated. Mitochondrial and nuclear markers are used to infer phylogenetic relationships between 31 genetically identified species. The monophyly of Apistogramma is suggested, and Apistogramma species are distributed into four clades, corresponding to three morphological lineages. Divergence times estimated with the Yule process and an uncorrelated lognormal clock dated the Apistogramma origin to the beginning of the Eocene (≈ 50 Myr) suggesting that diversification might be related to marine incursions. Our molecular dating also suggests that the Quaternary glacial cycles coincide with the phases leading to Apistogramma speciation. These past events did not influence diversification rates in the speciose genus Apistogramma, since diversification appeared low and constant through time. Further characterization of processes involved in recent Apistogramma diversity will be necessary.

First description of nesting ecology of the endemic Grey-flanked Cinclodes Cinclodes oustaleti baeckstroemii from the Juan Fernández Islands, Chile

Abstract. The habitat and nest sites of an island-endemic, the Másafuera Grey-flanked Cinclodes, are described for the first time. The species breeds only in natural cavities in steep rock-walls and rocky slopes or ridges. The nest entrance diameter ranges from 5.5 to 20 cm, the nest chamber being placed within the rock so as to be invisible from the outside. The nest sites found — solely on Alejandro Selkirk Island — were located from a little above the sea-level to the summit region, the preferred habitats being barren canyon bottoms with small streams, and humid alpine plateaus. Nesting extends from early December to late January, indicating a core breeding season from November to January. Fledgling numbers per clutch average about two.