Mechanisms Creating Community Structure Across a Freshwater Habitat Gradient

Abstract

Lentic freshwater habitats in temperate regions exist along a gradient from small ephemeral ponds to large permanent lakes. This environmental continuum is a useful axis for understanding how attributes of individuals ultimately generate structure at the level of the community. Community structure across the gradient is determined by both (a) physical factors, such as pond drying and winter anoxia, that limit the potential breadth of species distributions, and (b) biotic effects mediated by ecological interactions, principally predation, that determine the realized success of species. Fitness tradeoffs associated with a few critical traits of individuals often form the basis for species turnover along the gradient. Among species that inhabit temporary ponds, distributions are often constrained because traits that enhance developmental rate and competitive ability also increase susceptibility to predators. In permanent ponds, changes in the composition of major predators over the gradient limit distributions of prey species because traits that reduce mortality risk in one region of the gradient cause increased risk in other regions of the gradient. Integrated across the gradient, these patterns in species success generate distinct patterns in community structure. Additionally, spatial heterogeneity among habitats along the gradient and the fitness tradeoffs created by this heterogeneity may hold important evolutionary implications for habitat specialization and lineage diversification in aquatic taxa. 337

Notonectaexhibit threat-sensitive, predator-induced dispersal

“…It is well documented that fish can have strong effects on community structure (Wellborn et al 1996). These include both the direct effects of mortality within habitats, and the effects of predatorinduced dispersal within continuous habitats.…”

Metacommunity dynamics of amphibians in years with differing rainfall

“…water depth, salinity; Welborn et al 1996;hydroperiod;Snodgrass et al 2000;number of predators;Van Buskirk 2005;pond size, vegetation;Vági et al 2013) and landscape variables (e.g. forest cover, proportion of open landscape; Van Buskirk 2005;Richter-Boix et al 2007) are both important in shaping amphibian communities.…”

Riqueza e distribuição temporal de anuros (Amphibia: Anura) em um fragmento de Floresta Ombrófila Mista

“…Estudos onde a temperatura e a precipitação não influenciaram a diversidade da anurofauna mostraram que fatores normalmente não analisados, como fotoperíodo (boTh et al, 2008) Pombal Jr & haDDaD (2005). A riqueza mais alta do ambiente PTF pode ser atribuída pelo fato da inexistência de peixes que são predadores de girinos e podem ter uma forte influência negativa sobre a taxocenose, independentemente da espécie de peixe ocorrente ser nativa (Wellborn et al, 1996;hecnar & m'closKey, 1997) ou introduzida (PillioD et al 2010). Outra possibilidade é que a heterogeneidade ambiental seja um fator importante, já que o ambiente PTF era visivelmente o mais heterogêneo, fornecendo assim uma maior variedade de microhabitat que foram utilizados por diferentes espécies, aumentando a riqueza local (vasconcelos et al, 2009).…”