Maciej Ejsmond

Storing of internal reserves for reproduction and its role in animal invasions

Species expansions represent an important part of global change and are an unavoidable consequence of ecological and socioeconomic processes. Spreading of non-native animal species into new geographical regions reduces biodiversity due to extinction of native species and exerts tremendous negative economic impact with estimated annual costs of billions of dollars. Hence, managing of events of biological invasions is one of the most important challenges in conservation biology and ecology nowadays. In this project, we will create mathematical models of biological invasions and perform comparative analyses of fish species to identify the role of so-called capital breeding, i.e. storing of internal reserves for reproduction, in animal invasions. With general implications derived from our models, we will perform comparative analyses for fish species, as for this taxonomic group there is extensive literature data on the degree to which internal reserves are used in reproduction group. Capital breeding has received a little attention in studies of biological invasions and range shifts. Does storing of internal reserves for reproduction facilitate or impede successful animal invasions? Which environmental circumstances promote invasions by species that store for reproduction? Which species among those who store and do not store for reproduction are better invaders? The state-of-the-art of the invasion biology and ecology does not allow to answer these questions and our aim is to fill the gap by using theoretical modelling and comparative analyses.

We will develop mathematical models of life cycles of hypothetical animals. The modelled organisms will adopt various reproductive strategies, differing in the build-up of internal reserves before reproduction. The models will find reproductive strategies that cannot be overcompeted by individuals applying alternative breeding tactics, and will simulate subsequent phases of biological invasions and different aspects of range shifts. We will expose modelled species to various regimes of seasonal variation in conditions and thermal regimes. These seasonal changes of conditions will be translated into trends in survival chance of the produced offspring. Our models will allow us to test to what extent seasonality can increase the potential of capital breeders to be the best invaders, i.e. grow in population number faster than organisms adopting alternative breeding strategies. Conclusions derived from theoretical models will be tested with comparative analyses of fish species. With these analyses we will test how invasion potential of fish species depend on the adopted strategy of storing internal reserves for reproduction. Our analyses will take into account phylogenetic relationships between species.

The main motivation for running the proposed research is the lack of an ecological theory that would allow to understand historical, explain ongoing, and forecast upcoming animal invasions and climate-induced range shifts in relation to the diversity of breeding tactic based on storing for future reproduction. Current scientific literature provides contradictory predictions regarding the invasive potential of capital breeders. In some cases, storing for future reproduction slows down growth of population number and can be regarded as a trait that supress the invasive potential. However, there are many examples of invasions by species that store reserves for reproduction, with capital breeding crustaceans or amphibians being among the most harmful invaders. Biological invasions are characterized by a sequence of phases, with a stationary phase of establishment of a non-native species preceding the phase of a rapid expansion and increase in population number. Actions taken during the stationary phase, sometimes lasting several years, significantly increase chances of reducing negative impact of the invasion in the future. Conservation biology seeks for candidate traits that predispose non-native animal species to switch from stationary to rapid expansion phase of invasion. Our motivation is to test if capital breeding is one of such traits.

We will create a comprehensive theory, supported with comparative analyses, that allows understanding of the role of capital breeding in animal invasions and range shifts. We will also answer questions asked in the first paragraph of this summary. Our results will identify the degree of seasonal changes in conditions that augment invading potential of species adopting capital breeding. The formed theory and analyses will allow to forecast the fate of biological invasion by animals that differ in the degree to which internal reserves are used for reproduction.