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A team of experienced lepidopterists sampled the butterfly fauna of Peru’s Cosñipata Region from 400 to 4,000 m elevation for more than a decade (7,440 field person hours) and supplemented this sample with data from museum specimens and the scientific literature. An annotated checklist of Cosñipata Riodinidae (Lepidoptera: Papilionoidea) documents 398 species, which represents 29% of the world Riodinidae fauna. For each, it lists sample abundance, adult behavior, elevation, and temporal distribution. In the fieldwork sample, 75 species (20.9%) were sampled once and 39 (9.8%) were not encountered (collected or imaged by others). A riodinid species of median abundance was sampled an average of once every 826 field person-hours. Sampled sex ratios were 81.2% male, but were not statistically higher in species in which male perching behavior was observed. We document examples of conspicuous geographic variation in the time of male perching behavior. Species richness is greatest at low elevation and at the transition between the dry and wet seasons. There is little evidence that the community is composed of species restricted to narrow elevational bands or restricted in the adult stage to a single season. Compared with Lycaenidae, Riodinidae are significantly more restricted to lowland habitats and were sampled 2.5 times as frequently with a mean number of individuals per species more than twice as great as that of Lycaenidae.
ZooBank registration. urn:lsid:zoobank.org:pub:51233294-9511-41E4-980F-5A0D9080C680
The extent of male mate choosiness is driven by a trade-off between various environmental factors associated with the costs of mate acquisition, quality assessment and opportunity costs. Our knowledge about natural variation in male mate choosiness across different populations of the same species, however, remains limited. In this study, we compared male mate choosiness across 10 natural populations of the freshwater amphipod Gammarus roeselii (Gervais 1835), a species with overall high male mating investments, and evaluated the relative influence of population density and sex ratio (both affecting mate availability) on male mate choosiness. We investigated amplexus establishment after separating mating pairs and presenting focal males with a novel, size-matched female from the same population. Our analysis revealed considerable effects of sex ratio and (to a lesser extent) population density on time until amplexus establishment (choosiness). Male amphipods are able to perceive variable social conditions (e.g., sex ratio) and modify their mating strategy accordingly: We found choosiness to be reduced in increasingly male-biased populations, whereas selectivity increases when sex ratio becomes female biased. With this, our study expands our limited knowledge on natural variations in male mate choosiness and illustrates the importance of sex ratio (i.e., level of competition) for male mating decisions in natural environments. Accounting for variation in sex ratios, therefore, allows envisioning a distinctive variation of choosiness in natural populations and highlights the importance of considering social background information in future behavioral studies.
Wir untersuchten eine Kolonie der Brückenspinne Larinioides sclopetarius (Clerck, 1757) an einem Strassendamm im Innenhafen von Duisburg. Die Studie fand zwischen März und Oktober 2004 statt. Die mittlere Populationsdichte über alle Größenklassen betrug 26,2 Ind./qm, das absolute Maximum wurde im Juli festgestellt (71,3 Ind./qm). Die kleinsten Juvenilstadien fanden wir hauptsächlich von Juni bis Oktober, mit einer maximalen mittleren Dichte von 30,9 Ind./qm im Juli, so dass man auf den Sommer als Schlupftermin schließen kann. Große Männchen und Weibchen gab es bereits vereinzelt im Frühjahr, allerdings wurden die höchsten Abundanzen (mit mehr als 3 Ind./qm je Geschlecht) im Sommer und Herbst erreicht. Das durchschnittliche Geschlechtsverhältnis der adulten Spinnen lag über die gesamte Untersuchungszeit gesehen bei 1:1,2 (männl.:weibl.). Es werden einige Vergleiche mit anderen Araneiden, darunter solitäre und soziale Arten, gezogen.