Seasonal availability of resources and habitat degradation for the western tree-hole mosquito, Aedes sierrensis

Abstract

The nutrient base of aquatic tree-hole communities is derived from leaf litter, benthic detritus, and water flowing down the tree trunk (stemflow water). Previous studies in eastern North America with the mosquito, Aedes triseriatus, have identified leaf litter as a major and stemflow water as a minor source of mosquito nutrition, but did not consider the role of the benthic detritus or how the aggregate or relative contribution of these sources of mosquito nutrition changed during the year. We use the leaf litter, benthic detritus, and stemflow water from tree holes in western Oregon (USA) to determine how these substrates affect mass at metamorphosis, biomass yield, and fitness (cohort replacement rate; R ) of the mosquito, Aedes sierrensis, through both natural and simulated winters, the normal growing season for larvae in tree holes. We found that fresh leaf litter constitutes the major determinant of mosquito fitness by a factor of>15:1 over any other substrate taken directly from tree holes in nature. The other substrates, including the benthic detritus, individually make only a meager contribution to mosquito fitness but, when added to the leaf litter, can sustain yield and improve fitness at high, limiting larval densities. Nutritional quality of tree-hole substrates declines by >90% from early (fall) to late (spring) in the larval growing season. At both times of year, the coarse or fine detritus provide minor resources, and stemflow water provides no detectable contribution to mosquito nutrition. The resources in the litter are not transported during the year to the benthic detritus; rather, these resources are either exploited by mosquitoes when they first become available, or they deteriorate and become progressively more unavailable to them. Growth and development of A. sierrensis feeding on dried and reconstituted tree-hole contents during a 6-month simulated winter in the laboratory showed: (1) the same relative contributions of leaf litter, benthic detritus, and stemflow water to mosquito nutrition, (2) that the winter deterioration of substrate quality is a direct consequence of microbial decomposition, and (3) that pre-emptive competition from pre-existing A. sierrensis greatly increases substrate deterioration. We conclude that the progressive winter deterioration of larval resources in combination with the dry summers of western North America are the most likely environmental factors that limit species diversity in tree holes and that have selected for early recruitment (autumnal hatching) of A. sierrensis and for its univoltine life cycle from Mexico to Canada.

Variability of intra‐ and interspecific competitions of bamboo stump mosquito larvae over small and large spatial scales

“…A positive relationship between productivity and species diversity was reported for tree‐hole communities (Srivastava and Lawton 1998). In the present study, a significant effect of litter on pupation of A. albopictus was detected, which confirmed the importance of litter as a limiting factor of mosquito production, as reported by several authors for tree hole mosquitoes (Carpenter 1982, 1983, Léonard and Juliano 1995, Yanoviak 1999, Maciá and Bradshaw 2000). However, we found no evidence that interspecific competition was less severe in litter‐rich microcosms.…”

Soluble nutrient effects on microbial communities and mosquito production in Ochlerotatus triseriatus habitats

“…Although initial leaf input is critical for larvae (Carpenter 1983, Leonard & Juliano 1995, this resource may degrade in quality rapidly (Macia & Bradshaw 2000), thereby intensifying larval competition during development. Stemflow inputs alone are relatively unimportant in determining mosquito production compared to leaf material (Macia & Bradshaw 2000), but can be important modifiers of leaf decay and mosquito performance (Carpenter 1982). Periodic supplements from stemflow or additional particulate input during leaf quality decline are probably critical in allowing continued development of larvae in treehole habitats.…”

Interactions with native mosquito larvae regulate the production of Aedes albopictus from bromeliads in Florida

“…Priority effects demonstrated by Sunahara and Mogi (2002) for competition between T. bambusa and A. albopictus in bamboos have also been observed among other systems involving larval mosquitoes (e.g. Livdahl, 1982; Blaustein & Margalit, 1996; Maciá & Bradshaw, 2000).…”