Getting there and around: Host range oscillations during colonization of the Canary Islands by the parasitic nematode Spauligodon

Abstract

Episodes of expansion and isolation in geographic range over space and time, during which parasites have the opportunity to expand their host range, are linked to the development of host-parasite mosaic assemblages and parasite diversification. In this study, we investigated whether island colonization events lead to host range oscillations in a taxon of host-specific parasitic nematodes of the genus Spauligodon in the Canary Islands. We further investigated whether range oscillations also resulted in shifts in host breadth (i.e., specialization), as expected for parasites on islands. Parasite phylogeny and divergence time estimates were inferred from molecular data with Bayesian methods. Host divergence times were set as calibration priors after a priori evaluation with a global-fit method of which individual host-parasite associations likely represent cospeciation links. Parasite colonization history was reconstructed, followed by an estimation of oscillation events and specificity level. The results indicate the presence of four Spauligodon clades in the Canary Islands, which originated from at least three different colonization events. We found evidence of host range oscillations to truly novel hosts, which in one case led to higher diversification. Contemporary host-parasite associations show strong host specificity, suggesting that changes in host breadth were limited to the shift period. Lineages with more frequent and wider taxonomic host range oscillations prior to the initial colonization event showed wider range oscillations during colonization and diversification within the archipelago. Our results suggest that a lineage's evolutionary past may be the best indicator of a parasite's potential for future range expansions.

Gene flow between island populations of the malaria mosquito, Anopheles hinesorum, may have contributed to the spread of divergent host preference phenotypes

“…hinesorum to ectothermic hosts. Other animals, including insects, have experienced host shifts and specialization when colonizing islands (Jorge et al, 2018; Simberloff, 1974; Tseng et al, 2018; Yassin et al, 2016), and the Solomon Archipelago supports an abundant and diverse frog and reptile fauna (Morrison et al, 2007; Pikacha et al, 2016), providing an plentiful potential food source.…”

Identifying co-phylogenetic hotspots for zoonotic disease

“…At these large geographical and temporal scales, it is possible that relatively fast-evolving helminth lineages are little constrained in their host use by their own phylogenetic history [60,61]. It is possible that the signature of phylogenetic conservatism in host use on the helminth phylogeny would be more apparent at finer geographical scales and within more recently formed hosts assemblages [49,[62][63][64][65]. Indeed, there is evidence that host movement can generate genetic structure in nematode parasites [66] and presumably, if host populations remain separated, we would expect parasite populations to become reproductively isolated.…”

Where are we in the host-parasite relationships of native land vertebrates in Macaronesia?

“…Estas aproximaciones nos permitirán entender por qué unas especies de parásitos son más exitosas que otras, o desenredar historias evolutivas complejas sabiendo que hospedadores y parásitos colonizaron las islas al mismo tiempo (Illera et al 2015). En reptiles, por ejemplo, la comparación entre los patrones observados en hemogregarinas y nematodos del género Spauligodon (que presenta un ciclo de vida directo con un único hospedador) son extremadamente interesantes (Jorge et al 2018;Tomé et al 2018). Por un lado, los dos parásitos presentan elevada diversidad y especificidad por los hospedadores intermediarios, pero por otro, los nematodos presentan una capacidad mayor para saltar de hospedador, aunque de forma temporal.…”