Biochemical and physiological data collection

Physiological and biochemical traits hold great promise for demographic research as potential proxies (biomarkers) of various biotic and environmental variables that determine individual fitness and ultimately demographic rates. Integrating such biomarkers into demographic models can thus provide insights into drivers of population dynamics or increase predictive power of the models by refining estimation of vital rates. Biomarkers also represent promising means to characterise population structure and dynamics on much shorter time-scales compared to classical demographic approaches. Functional traits further emerge as direct targets of conservation efforts directed towards conserving functional diversity. Yet, biomarkers and functional traits remain underutilised in demography and population ecology, indicating that their benefits still await wider recognition. This chapter briefly reviews the most prominent physiological and biochemical traits (e.g. metabolic rates, hormones, oxidative stress markers, telomeres) that may be of interest in animal and plant demographic research, including the methods for collection, storage, and analysis, and the criteria to be met before the trait is validated as a biomarker. Hopefully, this effort will stimulate further integration of physiological and biochemical data into demographic framework.

Abalone populations are most sensitive to environmental stress effects on adult individuals

Marine organisms are exposed to stressors associated with climate change throughout their life cycle, but a majority of studies focus on responses in single life stages, typically early ones. Here, we examined how negative impacts from stressors associated with climate change, ocean acidification, and pollution can act across multiple life stages to influence long-term population dynamics and decrease resilience to mass mortality events. We used a continuous-size-structured density-dependent model for abalone (Haliotis spp.), calcifying mollusks that support valuable fisheries, to explore the sensitivity of stock abundance and annual catch to potential changes in growth, survival, and fecundity across the organism’s lifespan. Our model predicts that decreased recruitment from lowered fertilization success or larval survival has small negative impacts on the population, and that stock size and fishery performance are much more sensitive to changes in parameters that affect the size or survival of adults. Sensitivity to impacts on subadults and juveniles is also important for the population, though less so than for adults. Importantly, likelihood of recovery following mortality events showed more pronounced sensitivity to most possible parameter impacts, greater than the effects on equilibrium density or catch. Our results suggest that future experiments on environmental stressors should focus on multiple life stages to capture effects on population structure and dynamics, particularly for species with size-dependent fecundity.

Extraguild prey availability reduced cannibalism and reciprocal intraguild predation of Neoseiulus barkeri (Acari: Phytoseiidae) and Scolothrips takahashii (Thysanoptera: Thripidae)

Cannibalism and intraguild predation (IGP) are two common interactions occurs in animal kingdom which influence their population structure and dynamics. Neoseiulus barkeri (Hughes) and Scolothrips takahashii (Priesner) are important natural enemies of citrus red mite Panonychus citri (McGregor). However, little was known about their interactions and how the availability of extraguild (EG) prey P. citri modulated their interactions. In this study, we determined incidences of cannibalism and intraguild predation of these two predators when different densities of extraguild prey P. citri were available. Our results showed that incidences of both cannibalism and IGP and were significantly reduced in the presence of the extraguild prey. The intraguild predation between N. barkeri and S. takahashii was bidirectional, but N. barkeri was a predominant intraguild predator over S. takahashii. The S. takahashii fed on immobile N. barkeri egg, and N. barkeri fed on inactive prepupa and pupa of S. takahashii, but the conspecifics seldom did. Our results indicated that the interactions of predators decreased significantly when prey was available. The predatory mite N. barkeri was a stronger interspecific competitor. The results of this study may be useful in developing effective biological control strategies against P. citri.