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Genetic variability of red swamp crayfish reveals its invasion process

Patterns of genetic diversity in invasive populations can be modulated by a range of factors acting at different stages of the invasion process, including the genetic composition of the source population(s), the introduction history (e.g. propagule pressure), the environmental suitability of recipient areas, and the features of secondary introductions. The North American red swamp crayfish, Procambarus clarkii, is one of the most widely introduced freshwater species worldwide. It was legally introduced into Spain twice, near the city of Badajoz in 1973 and in the Guadalquivir marshes in 1974. Thereafter the species rapidly colonised almost the entire Iberian Peninsula. Seven nuclear microsatellites were used to describe the genetic diversity and structure of 28 locations distributed across the Iberian Peninsula and to explain the expansion process of the red swamp crayfish. Additionally, the relationship between environmental suitability and genetic diversity of the studied locations were analysed. The red swamp crayfish had a clear spatial genetic structure in the Iberian Peninsula, probably determined by the two independent introduction events in the 1970s, which produced two main clusters separated spatially, one of which was dominant in Portugal and the other in Spain. The human-mediated dispersal process seemed to have involved invasion hubs, hosting highly genetically diverse areas and acting as sources for subsequent introductions. Genetic diversity also tended to be higher in more suitable environments across the Iberian Peninsula. These results showed that the complex and human-mediated expansion of the red swamp crayfish in the Iberian Peninsula has involved several long- and short-distance movements and that both ecological and anthropogenic factors have shaped the genetic diversity patterns resulting from this invasion process. Early detection of potential invasion hubs may help to halt multiple short-distance translocations and thus the rapid expansion of highly prolific invasive species over non-native areas. informacion[at] Acevedo-Limón et al (2020) Historical, human, and environmental drivers of genetic diversity in the red swamp crayfish (Procambarus clarkii) invading the Iberian Peninsula. Freshwater Biology. Doi 10.1111/fwb.13513
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The costs of nestling begging behavior

The costs of nestling begging behavior

Many theoretical models on the evolution of nestling begging assume this behavior is costly, so that only nestlings in real need of food would profit from giving intensive signals to parents. However, evidence accumulated for the last 2 decades is either contradictory (growth costs) or scant (immunological cost). Here, the existence of both costs is experimentally tested in pied flycatcher nestlings, a species in which parents appropriately respond to honest begging signals. Nestlings were paired by nest of origin and similar body mass. In each pair, a nestling was forced to beg for 51s/meal, whereas the other begged for only 3.4s/meal, both receiving the same amount of food. Simultaneously, the nestling immune response to an antigen (phytohemagglutinin) was measured. Experimental nestlings showed reduced immunocompetence compared with control chicks, which in this species could be regarded as a genuine direct cost. High-begging nestlings also gained less mass during the daylight activity hours. However, they lost less mass while resting at night, resulting in similar mass gains for both groups across the whole daily cycle. This suggests that negative effects of excess begging on mass gain can be compensated for by nestlings, thus avoiding the negative fitness consequences (i.e., cost) of a retarded growth. Mixed results found in previous studies may reflect interspecific differences in compensatory changes in mass gain. But if such differences do not map into fitness consequences, they may be of little help to answer the question of whether begging entails direct growth costs. Redondo et al (2016) Pied flycatcher nestlings incur immunological but not growth begging costs. Behav Ecol doi: 10.1093/beheco/arw045