Persistence of multiple identical parasitoid species in a single-host, spatial simulation

Abstract

Multiple parasitoids, including multiple obligate specialists, often coexist on a single host (for example Hawkins 1993b, Memmott et al. 1994. Explanations of parasitoid coexistence generally stipulate some difference between the competitors that allows them to exploit different resources, or a mechanism that allows for spatial or temporal differences in their attacks. In the case of specialist parasitoids with the same host, the differences are often subtle.There have been a number of articles discussing mechanisms or models developed to explain the continued coexistence of such parasitoids, or similarly, of competitors for a single resource. A prevalent theme is that of a behavioral mechanism or physiological difference between competing species, such as a trade-off between dispersal and searching abilities, or a variation on this theme (Hassell et al. 1994, Comins and Hassell 1996, Ruxton and Rohani 1996. Similarly, in a source-sink resource flow, Loreau and DeAngelis (1997) showed that a tradeoff between exploitative and interference ability led to a partitioning of resources, and continued coexistence of competitors. Amarasekare (2000) demonstrated a similar tradeoff between local searching ability and competitive (intraguild predation) power, but on a local level. We explore the problem of persistence of multiple obligate parasitoids on a single host in a discrete time, spatially explicit system. In general, the parasitoids experienced extinction until one species remained well before the 50000-generation time limit, but the rate varied according to the parameters of the system. Smaller arenas had a greater chance of extinction. Artificially increasing interspecific competition produced rapid extinction, while decreasing competition increased persistence to the maximum time limit of the simulation. Increasing the parasitoid search efficiency or decreasing dispersal of the parasitoids relative to the host produced less longevity as did increasing host reproduction, while increasing the rate of "patch extinction" reduced the variation among the times to extinction, but did not change the time to the first extinction. Finally, increasing noise in the search parameter first reduced longevity, but then it rapidly increased near the point where the noise reached an amplitude similar to the parameter itself, where coexistence of the four parasitoids was achieved.

Co-occurrence in ant primary parasitoids: a Camponotus rectangularis colony as host of two eucharitid wasp genera

“…In addition to factors that influence the spatial distribution of parasitoids at the landscape and local level ( Kruess, 2003 ; see Cronin & Reeve, 2005 for a review), the stable co-existence of multiple parasitoid species attacking the same host species is generally explained (but see Berry & Widder, 2014 ; Freilich et al, 2018 ; Blanchet, Cazelles & Gravel, 2020 ) by spatial or temporal niche differentiation ( Zhang et al, 2021 ). Parasitoid coexistence usually involves differences between competitors in at least some of their natural history traits, allowing them to either exploit different sources or to exploit the same resource but using spatial or temporal differences in their attacks ( Hassell, Comins & May, 1994 ; Comins & Hassell, 1996 ; Amarasekare, 2000 ; Slone & Allen, 2005 ; Zhang et al, 2021 ). Theoretical and empirical evidence suggests that species with similar ecological requirements tend to interact strongly, leading to negative species interactions or competitive exclusion ( Godfray, 1994 ).…”

“…Theoretical and empirical evidence suggests that species with similar ecological requirements tend to interact strongly, leading to negative species interactions or competitive exclusion ( Godfray, 1994 ). However, in the case of phylogenetically related specialist parasitoids that attack the same host species and the same developmental stage, the differences between competitors may be very small or subtle and, therefore, more difficult to specify ( Slone & Allen, 2005 ). Such co-occurrence of specialized ant parasitoids has already been reported at the population and colony levels for closely related eucharitid wasp species sharing similar niches ( Pérez-Lachaud et al, 2006 ; Pérez-Lachaud & Lachaud, 2014 ), and even in the same individual ant host (multiparasitism) ( Pérez-Lachaud, López-Méndez & Lachaud, 2006 ).…”

Generalized conditions for coexistence of competing parasitoids on a shared host

“…densities across generations. Future work will focus on incorporating correlations in the attack rate, allowing for one of the parasitoid to have a Type III functional response (which can also be strongly stabilizing [19]), and also exploring spatial mechanism for parasitoid coexistence [43]- [46].…”