L A van Boheemen
Monash University, School of Biological Sciences, Graduate Student
In cooperatively breeding species, care provided by helpers may affect the dominant breeders’ investment trade‐offs between current and future reproduction. By negatively compensating for such additional care, breeders can reduce costs of... more
In cooperatively breeding species, care provided by helpers may affect the dominant breeders’ investment trade‐offs between current and future reproduction. By negatively compensating for such additional care, breeders can reduce costs of reproduction and improve their own chances of survival. Alternatively, helper care can be additive to that of dominants, increasing the fledging fitness of the current brood. However, the influence helpers have on brood care may be affected by group size and territory quality. Therefore, the impact of helping needs to be disentangled from other factors determining offspring investment before conclusive inferences about the effect of help on additive and compensatory care can be made. We used 20 years of provisioning data to investigate the effect of helping on provisioning rates in the facultative cooperatively breeding Seychelles warbler Acrocephalus sechellensis. Our extensive dataset allowed us to statistically disentangle the effects of helper presence, living in larger groups and different food availability. We show compensatory and additive care (i.e., partial compensation) in response to helper provisioning. Helpers lightened the provisioning load of the dominant male and female and increased total provisioning to nestlings. This was irrespective of group size or territory quality (food availability). Moreover, our results illustrate sex‐specific variation in parental care over the course of the breeding event. We discriminate between temporal variation, group size, and territory quality processes affecting cooperative care and as such, gain further insight into the importance of these factors to the evolutionary maintenance of helping behavior.
1. Traditionally, studies on vegetation succession have focused either on plant–plant interactions or on interactions between plants and their physical environment, for example through organic matter build-up and increased nutrient... more
1. Traditionally, studies on vegetation succession have focused either on plant–plant interactions or on interactions between plants and their physical environment, for example through organic matter build-up and increased nutrient cycling. These interactions can change conditions for macrodetriti-vores that feed on plant litter, but their role in vegetation succession is rarely studied. In this paper, we explore whether the bioturbating crustacean macrodetritivore Orchestia gammarellus alters soil conditions in a saltmarsh ecosystem in such a way that it promotes late-successional, less stress-tolerant plant species at the expense of early successional species. 2. To answer this, we performed a field and a laboratory experiment in which we manipulated abundances of O. gammarellus, and studied the consequences for soil physical and chemical parameters and for vegetation community composition. 3. Our field experiment showed that O. gammarellus stimulated nitrogen mineralization, likely resulting from the positive effect of this macrodetritivore on soil aeration and litter decomposition. Moreover, results from the laboratory experiment showed that O. gammarellus negatively affected dicot seedling survival of mainly early successional plant species, likely through grazing, thus affecting plant community composition. 4. The experiments together provided evidence that O. gammarellus promotes late-successional plant species in multiple ways: by alleviation of anoxic conditions, by promoting nutrient cycling and by selective herbivory on early successional species. 5. Synthesis. By demonstrating that a species traditionally considered as part of the detrital ('brown') food web is thus an important accelerator of vegetation succession, this study documents an important but often overlooked link in food web and ecosystem ecology.
Research Interests:
Admixture between differentiated populations is considered to be a powerful mechanism stimulating the invasive success of some introduced species. It is generally facilitated through multiple introductions; however, the importance of... more
Admixture between differentiated populations is considered to be a powerful mechanism stimulating the invasive success of some introduced species. It is generally facilitated through multiple introductions; however, the importance of admixture prior to introduction has rarely been considered. We assess the likelihood that the invasive Ambrosia artemisiifolia populations of Europe and Australia developed through multiple introductions or were sourced from a historical admixture zone within native North America. To do this, we combine large genomic and sampling datasets analyzed with approximate Bayesian computation and Random Forest scenario evaluation to compare single and multiple invasion scenarios with pre- and post-introduction admixture simultaneously. We show the historical admixture zone within native North America originated before global invasion of this weed, and could act as a potential source of introduced populations. We provide evidence supporting the hypothesis that the invasive populations established through multiple introductions from the native range into Europe and subsequent bridgehead invasion into Australia. We discuss the evolutionary mechanisms that could promote invasiveness and evolutionary potential of alien species from bridgehead invasions and admixed source populations.