Compensatory recruitment allows amphibian population persistence in anthropogenic habitats

Abstract

Habitat anthropization is a major driver of global biodiversity decline. Although most species are negatively affected, some benefit from anthropogenic habitat modifications by showing intriguing life-history responses. For instance, increased recruitment through higher allocation to reproduction or improved performance during early-life stages could compensate for reduced adult survival, corresponding to “compensatory recruitment”. To date, evidence of compensatory recruitment in response to habitat modification is restricted to plants, limiting understanding of its importance as a response to global change. We used the yellow-bellied toad ( Bombina variegata ), an amphibian occupying a broad range of natural and anthropogenic habitats, as a model species to test for and to quantify compensatory recruitment. Using an exceptional capture–recapture dataset composed of 21,714 individuals from 67 populations across Europe, we showed that adult survival was lower, lifespan was shorter, and actuarial senescence was higher in anthropogenic habitats, especially those affected by intense human activities. Increased recruitment in anthropogenic habitats fully offset reductions in adult survival, with the consequence that population growth rate in both habitat types was similar. Our findings indicate that compensatory recruitment allows toad populations to remain viable in human-dominated habitats and might facilitate the persistence of other animal populations in such environments.

Tastier than thought? Telemetric research reveals predation on the poisonous yellow‐bellied toad Bombina variegata

“…The yellow-bellied toad can live for more than 20 years in the wild (Szymura & Pabijan, 2018), and its longevity has usually been attributed to its toxicity and lack of natural enemies (Hossie et al, 2013;Szymura & Pabijan, 2018). Although known variations in longevity among populations are reported to have been caused by various factors, mainly anthropogenic ones (Cayuela et al, 2022), the predation levels reported here can influence local populations strongly enough to cause differences in demography among them. This is in line with a new hypothesis that relates demographic differences among toad populations to variations in predation caused by different levels of chemical defense (Hantzschmann et al, 2019).…”

Land-use preferences of the European green toad (Bufotes viridis) in the city of Vienna (Austria): the importance of open land in urban environments

“…Such tolerance, to salt and other pollutants, may help them to inhabit urban environments. However, a study in Germany indicated that anthropogenic land-use changes are reducing the green toads’ lifespan [ 30 ], hence, breeding success would need to counteract such effect in order to maintain stable populations [c.f., 31 ].…”

Despite early deaths, toads persist in human-dominated habitats

“…However, with still further anthropogenic pressure beyond those quantified by Cayuela et al. ( 2 ), populations may eventually be unable to produce enough young to compensate for the heightened mortality they experience, leading to a threshold effect and population collapse.…”

“…In PNAS, Cayuela et al. ( 2 ) do just this by examining how the yellow-bellied toad ( Bombina variegata ) maintains viable populations in human-dominated habitats.…”

“… Schematic of the recruitment compensation documented by Cayuela et al. ( 2 ) depicting how increasing the levels of human environmental modification ( x axis) affects key demographic rates of survival, recruitment, and overall population growth ( y axis). Populations are stable when growth rate is equal to one, increase when growth rate is above one, and decrease when it is below one.…”