Measuring and modeling dispersal of adult zooplankton

Abstract

Habitat fragmentation poses an inherent problem for metacommunity dynamics, as dispersal among communities is hindered by increasing isolation and the loss of patches. Wetlands are one such system that have undergone excessive destruction and fragmentation in recent years. Zooplankton within these communities have historically been considered frequent and widespread dispersers, but direct, quantitative measures of zooplankton dispersal are rare. In this study, I performed two experiments to quantify zooplankton dispersal and to identify the primary dispersal vectors. I first set up an array of traps at 10, 30, 60, 120 and 180 m around an isolated pond to collect dispersing individuals. Nearly 1,500 adult zooplankton were captured in traps up to 180 m from the pond, with approximately 60% of dispersers being captured in traps at 10 m from the pond. A second experiment using open and animal-excluded traps suggested that large animals were the primary dispersal vector for these zooplankton. Using a subset of these data, I fit four models to describe the shape and magnitude of adult cladoceran dispersal at this site. All models showed the majority of cladocerans were deposited very close to the source pond, with three models suggesting that the trapping area encompassed 67% or more of the dispersal distances. These results suggest that adult zooplankton movement among ponds may be significant in areas where aquatic habitats are plentiful. Yet, in recent years climate change and anthropogenic disturbances have reduced the number and size of aquatic habitats in many regions of the world, likely curtailing effective transport of individuals in many cases. As a result, fragmented zooplankton metacommunities may experience increased dispersal limitation, stronger priority effects, higher levels of inbreeding and selection against traits engendering high dispersability.

How do freshwater organisms cross the “dry ocean”? A review on passive dispersal and colonization processes with a special focus on temporary ponds

“…As suggested by Allen (2007), this reduction might lead to stronger priority effects (see next subchapter), higher levels of inbreeding and selection against traits favouring high dispersability. Miracle (1982) and Sahuquillo & Miracle (2013), in order to explain the distribution of some peculiar crustacean assemblages in the ponds of the Iberian Peninsula, hypothesized the existence of a former and ancient network of wetlands which allowed the presence of highly diversified crustaceans assemblages.…”

“…However, the information contained in the scientific literature is sometime contradictory with some authors suggesting that wind can be more effective than animals as dispersal vector and some other stating the opposite (e.g. Cohen & Shurin, 2003;Allen, 2007).…”

“…Although papers documenting passive dispersal of adult microcrustaceans, water mites and plants are available in the literature (Dahms, 1995;Di Sabatino et al, 2004;Allen, 2007;Frisch & Green, 2007;van Leeuwen et al, 2013;Bruckerhoff et al, 2014), passive dispersal mechanisms more generally require the production of resting stages able to survive unfavourable environmental conditions and to act as dispersal propagules, functionally performing as plant seeds (see Van Damme & Sinev, 2013). Resting stages are the most important propagules for many aquatic taxa (Rundle et al, 2002) and are easily transported by different physical and biological vectors (Fig.…”

“…Conversely, a study aimed at assessing the dispersal of freshwater taxa among Mediterranean temporary ponds through epizoochory and endozoochory on\in wild boars (Vanschoenwinkel et al, 2008c) showed that, since these environments are frequently used for mud bathing by these mammals, a larger number of hatching taxa was recorded in the mud coming from the skin rather than from the faeces, thus suggesting that over short distances epizoochory transport can be more effective than endozoochory. The potential role of large vertebrates as dispersal vectors was also investigated by Allen (2007) who studied adult zooplankton dispersal and found that it was more successful (and colonization occurred) in mesocosms which were open to large vertebrates like deer or raccoons. Short-distance dispersal can be favoured by several other vertebrates such as cattle, rats, rabbits, amphibians and fish (e.g.…”

“…species or lineages already present in a community affect the establishment of later arriving immigrants) (Fig. 6) and are often considered as powerful inhibitors of colonization success (Shurin, 2000;Allen, 2007;Louette & De Meester, 2007;Symons & Arnott, 2014). In some conditions, however, as those occurring in autogenic succession, priority effects may have a facilitative role when a species arriving earlier at a site alters the biotic and abiotic characteristics in a way that enhance the colonization chances of a species arriving later (Connell & Slatyer, 1977).…”