SPATIAL DISTRIBUTION OF BRANCHINECTELLA MEDIA (CRUSTACEA, BRANCHIOPODA) IN A SALINE POND FROM “LA MANCHA HÚMEDA”: A CASE OF HABITAT SELECTION?
Branchinectella media is a commonly observed anostracan in Mediterranean temporary saline ponds. Despite its wide distribution, many aspects of its natural history are unknown or poorly studied. In this work, we seek to understand the main factors that influence the spatial distribution of juveniles and adults of B. media in a pond that belongs to the Manjavacas Pond Systems in the “La Mancha Húmeda” Nature Reserve in central Spain. We sampled on two dates, 29 November and 24 December, 2015. Environmental variables, such as pH, conductivity, temperature, depth and vegetation cover, were recorded at 20 defined sites in the pond. A hierarchical partition analysis was used to identify the independent contribution of each variable on the density of juveniles and adults, and for each sampling date separately. On the first date, the predictive variables associated with the distribution of juveniles and adults were conductivity and depth, respectively. The density of juveniles was lower at sites with high conductivity, whereas adults occurred preferentially in deeper pond sectors. On the second date few adults were sampled, and only juvenile density was positively associated with depth. The use of deeper areas is possibly related to predation given the constant presence of waterfowl that feed on the littoral. Other causes, such as adaptation to temporary habitats with high evaporation rates and time stress to mate and produce resistant eggs, may play an important role.