A sink host allows a specialist herbivore to persist in a seasonal source

Abstract

In seasonal environments, sinks that are more persistent than sources may serve as temporal stepping stones for specialists. However, this possibility has to our knowledge, not been demonstrated to date, as such environments are thought to select for generalists, and the role of sinks, both in the field and in the laboratory, is difficult to document. Here, we used laboratory experiments to show that herbivorous arthropods associated with seasonally absent main (source) habitats can endure on a suboptimal (sink) host for several generations, albeit with a negative growth rate. Additionally, they dispersed towards this host less often than towards the main host and accepted it less often than the main host. Finally, repeated experimental evolution attempts revealed no adaptation to the suboptimal host. Nevertheless, field observations showed that arthropods are found in suboptimal habitats when the main habitat is unavailable. Together, these results show that evolutionary rescue in the suboptimal habitat is not possible. Instead, the sink habitat functions as a temporal stepping stone, allowing for the persistence of a specialist when the source habitat is gone.

Effective specialist or jack of all trades? Experimental evolution of a crop pest in fluctuating and stable environments

“…However, it is crucial to recognize whether the mite has the potential to feed on other plant resources because wheat only serves as a temporary resource for the mites due to seasonal fluctuations. Recent research has shown that other plant species can serve as temporary reservoirs (stepping stones) for the mite (Laska et al, 2021 ), although no study to date has considered whether and how environmental heterogeneity can affect the mite pest potential.…”

“…However, this has not yet been confirmed for A. tosichella . Therefore, in fluctuating agricultural environments, the subsistence of A. tosichella populations most likely depends on their potential to use different plant resources, some of them being sink habitats that function as temporary stepping stones (Laska et al, 2021 ).…”

“…However, a recent study indicated that wild grass species (viz. smooth brome) may act only as a sink habitat that functions as a temporal steppingstone allowing for the persistence of a specialist when the source habitat is gone; however, evolutionarily rescue of the pest in such suboptimal habitat is not possible (Laska et al, 2021 ). The cited recent study and the results presented here strongly indicate that A. tosichella MT‐1 is a wheat specialist, rather than a grass generalist.…”

“…Its small size enables the species to be undetected when infesting commodities; additionally, it has the ability to spread over long distances in wind currents and possesses broad thermal tolerance, which improves the mite’s invasive potential (Kuczyński et al, 2016 ; Navia et al, 2013 ). The mite represents a useful model species in ecology and evolution because it favors easy laboratory manipulation and maintenance of populations, has a relatively short generation time (7–10 days in 22–27ºC), rapid population growth, amenability to experimental evolution, and responds well to standard laboratory rearing protocols (e.g., Karpicka‐Ignatowska et al, 2019 , 2021 ; Kuczyński et al, 2016 ; Laska et al, 2021 ).…”

Evolution in agricultural systems: Moving toward the understanding of complexity

“…However, it is becoming increasingly clear that, if you look close enough, no system is simple. Indeed, the genetic basis of pesticide resistance is more complex than previously thought (Ffrench‐Constant, 2013 ; Labbé et al, 2007 ), adaptation to host plants do not follow simple rules even in simple systems (Laska et al, 2021 ; Magalhães et al, 2014 ), and trophic interactions are not always organized into a trophic chain, even in agroecosystems (Rosenheim, 1998 ; Rosenheim et al, 1995 ; Van Rijn et al, 2002 ). Moreover, agricultural landscapes are changing, with the general understanding that relying on pesticides and monocultures is not only environmentally detrimental, but also not optimal for pest control and plant yield in the long term (Janssen & van Rijn, 2021 ).…”