Biology subjects

Botsch, J. C.

Publications and source records attributed to Botsch, J. C..

3 recordsLinked to original sources

bioRxiv2021

Dependence of an aquatic insect population on contemporaneous primary production

O_LICharacterizing the dynamics of energy flow through ecosystems requires quantifying the degree to which primary and secondary production are coupled. This coupling is expected to be tight in ecosystems with high internal production relative to external carbon and energy inputs. C_LIO_LIWe experimentally quantified the dependence of aquatic insect emergence on fresh primary production, specifically for the midge population in Lake Myvatn, Iceland. Using field mesocosms, we manipulated algal primary production by reducing light availability via shading. We then used dissolved oxygen incubations to estimate fluxes of carbon through photosynthesis (i.e., gross primary production or "GPP") over the course of the experiment. C_LIO_LIWe found that elevated GPP was associated with higher emergence rates of adults, as judged both by comparison of emergence across the experimental shading treatments and estimates of in situ GPP within the mesocosms. Furthermore, larger adults emerged earlier than smaller ones, suggesting that asymmetries in resource availability among individuals affected the timing of emergence. Nonetheless, midge emergence was substantial under light-limiting conditions, indicating that while midges benefit from primary production contemporaneous with larval development, they are also capable of completing their life cycles on carbon already existing in the organic matter pool. C_LIO_LIOur results show that even in systems with limited allochthonous inputs, contemporaneous primary production may be not necessary for high secondary production and insect emergence. Instead, consumers can develop from consumption of biomass derived from past autochthonous primary production. This suggests that primary production and consumer dynamics can be partially decoupled in time in systems that depend on internal production. C_LI

ecology↗

bioRxiv2021

Ecosystem engineering alters density-dependent feedbacks in an aquatic insect population

Ecosystem engineers have large impacts on the communities in which they live, and these impacts may feed back to populations of engineers themselves. In this study, we assessed the effect of ecosystem engineering on density-dependent feedbacks for midges in Lake Myvatn, Iceland. The midge larvae reside in the sediment and build silk tubes that provide a substrate for algal growth, thereby elevating benthic primary production. Benthic algae are in turn the primary food source for the midge larvae, setting the stage for the effects of engineering to feed back to the midges themselves. Using a field mesocosm experiment manipulating larval midge densities, we found a generally positive but nonlinear relationship between density and benthic production. Furthermore, adult emergence increased with the primary production per midge larva. By combining these two relationships in a simple model, we found that the positive effect of midges on benthic production weakened the negative density dependence at low to intermediate larval densities. However, this benefit disappeared at high densities when midge consumption of primary producers exceeded their positive effects on primary production through ecosystem engineering. Our results illustrate how ecosystem engineering can alter density-dependent feedbacks for engineer populations.

ecology↗

bioRxiv2021

Quantifying community responses to environmental variation from replicate time series

Time-series data for ecological communities are increasingly available from long-term studies designed to track species responses to environmental change. However, classical multivariate methods for analyzing community composition have limited applicability for time series, as they do not account for temporal autocorrelation in community-member abundances. Furthermore, traditional approaches often obscure the connections between responses at the community level and those for individual taxa, limiting their capacity to infer mechanisms of community change. We show how linear mixed models that account for group-specific temporal autocorrelation and observation error can be used to infer both taxon- and community-level responses to environmental predictors from replicated time-series data. Variation in taxon-specific responses to predictors is modeled using random effects, which can be used to characterize variation in community composition. Moreover, the degree of autocorrelation is estimated separately for each taxon, since this is likely to vary due to differences in their underlying population dynamics. We illustrate the utility of the approach by analyzing the response of a predatory arthropod community to spatiotemporal variation in allochthonous resources in a subarctic landscape. Our results show how mixed models with temporal autocorrelation provide a unified approach to characterizing taxon- and community-level responses to environmental variation through time.

ecology↗