Mechanisms of possible self-limitation in the invasive Asian shore crab Hemigrapsus sanguineus

Abstract

Population sizes of invasive species are commonly characterized by boom-bust dynamics, and self-limitation via resource depletion is posited as one factor leading to these boom-bust changes in population size. Yet, while this phenomenon is well-documented in plants, few studies have demonstrated that self-limitation is possible for invasive animal species, especially those that are mobile. Here we examined the invasive Asian shore crab Hemigrapsus sanguineus, a species that reached very high abundances throughout invaded regions of North America, but has recently declined in many of these same regions. We examined the relationship between diet, energy storage, reproduction, and growth in crabs collected from the New Hampshire coast. We show that energy storage and reproduction both increase with diet quality, while growth declines with diet quality. These results suggest that self-limitation may be a contributing factor to the recent declines of H. sanguineus at sites where this invader was once much more abundant. Further, these results suggest a diet-associated tradeoff in energy allocation to different vital rates, with a focus on reproduction when high quality resources are consumed, and a focus instead on growth when poor quality resources are consumed.

Dietary and Reproductive Traits of Two Brachyuran Crab Species

“…Upon collection, the samples were frozen and stored on dry ice at −80° C until dissection. Following dissection, the samples were dried at 65° C (see Griffen et al, 2020a for a complete description of sampling methods and for a more complete description of these two sites).…”

“…Due to the relatively low nutrient content, a greater volume of plant material is needed to meet the same metabolic requirements that can be met with a smaller volume of animal material (i.e., compensatory feeding), which results in a larger gut over time for more herbivorous individuals. Previous studies demonstrate that gut width is a reliable predictor of diet in individual crabs (Griffen & Mosblack, 2011;Griffen et al, 2012), as well as at the population level by comparing across sites with different levels of food availability (Cannizzo et al, 2017(Cannizzo et al, , 2020Griffen et al, 2020a).…”

“…Finally, gut size is a reliable predictor of diets of individual crabs for both of these species (Griffen & Mosblack, 2011;Griffen et al, 2012;Cannizzo et al, 2017Cannizzo et al, , 2020Griffen et al, 2020a).…”

“…Our study considers two brachyuran crab species, the Asian shore crab Hemigrapsus sanguineus and the mangrove tree crab Aratus pisonii . Both species are primarily herbivorous (Griffen et al, 2020a; Griffen et al, 2020b). H. sanguineus has an omnivorous diet that can include macroalgae and detritus, as well as amphipods, polychaetes, and juvenile shelled prey, such as barnacles, bivalves, and gastropods (Brousseau & Goldberg, 2007).…”

“…Like H. sanguineus, A. pisonii has been described as an opportunistic omnivore, feeding on animal material preferentially when it is available, while plant material still makes up the bulk of its diet (Erickson et al, 2008). Finally, gut size is a reliable predictor of diets of individual crabs for both of these species (Griffen & Mosblack, 2011; Griffen et al, 2012; Cannizzo et al, 2017, 2020; Griffen et al, 2020a).…”