Life-history change in disease-ravaged Tasmanian devil populations

Abstract

Changes in life history are expected when new sources of extrinsic mortality impact on natural populations. We report a new disease, devil facial tumor disease, causing an abrupt transition from iteroparity toward single breeding in the largest extant carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii), in which males can weigh as much as 14 kg and females 9 kg. This change in life history is associated with almost complete mortality of individuals from this infectious cancer past their first year of adult life. Devils have shown their capacity to respond to this diseaseinduced increased adult mortality with a 16-fold increase in the proportion of individuals exhibiting precocious sexual maturity. These patterns are documented in five populations where there are data from before and after disease arrival and subsequent population impacts. To our knowledge, this is the first known case of infectious disease leading to increased early reproduction in a mammal. The persistence of both this disease and the associated life-history changes pose questions about longer-term evolutionary responses and conservation prospects for this iconic species.carnivorous marsupial ͉ infectious cancer ͉ wildlife disease ͉ precocious breeding ͉ semelparity

Condition-dependent reproductive effort in frogs infected by a widespread pathogen

“…A functionally similar response to infection by B. dendrobatidis occurs in northern leopard frogs (Lithobates pipiens); the testes of infected males are larger and contain more sperm than those of uninfected males [15]. Studies on other taxa reveal that present reproductive effort can increase as life expectancy decreases [10][11][12][13][14][15][16][17][18]. In our study, however, calling activity did not increase in all infected frogs; we found that infected frogs in relatively poor condition were less likely to call than uninfected frogs.…”

“…Both male and female hosts can compensate for an increased risk of mortality imposed by an infection by increasing their investment in earlier reproduction. For example, among female hosts, Tasmanian devils (Sarcophilus harrisii) infected by a transmissible cancer mature and breed earlier [12], and crickets (Acheta domesticus) infected by a bacterium, and water fleas (Daphnia magna) infected by a microsporidian lay more eggs [13,14]. Among male hosts, frogs (Lithobates pipiens) infected by a fungus increase sperm production [15], flies (Drosophila nigrospiracula) infected by a parasitic mite, and amphipods (Corophium volutator) infected by trematodes increase reproductive effort [16,17], and beetles (Tenebrio molitor) infected by tapeworms provide higher quality nuptial gifts to their mates, thus increasing egg production [18].…”

Fitness Consequences of Infection by Batrachochytrium dendrobatidis in Northern Leopard Frogs (Lithobates pipiens)

“…Terminal investment has been empirically documented in other systems. For example, house sparrows injected with Paramyxo virus vaccine were more likely to lay a second clutch in a single season (Bonneaud et al 2004), male blue-footed boobies treated with liposaccharides to elicit an immune response had increased reproductive success (Velando et al 2006), and Tasmanian devil populations afflicted with devil facial tumor disease showed precocial reproduction (Jones et al 2008).…”

Transmissible cancer in Tasmanian devils: localized lineage replacement and host population response

“…The epidemiological pattern of DFTD at sites across eastern Tasmania, as the disease spread from its northeastern origin where it was first detected in 1996, is of a rapid increase in force of infection reaching a prevalence of more than 50% within 2-4 years after local epidemic outbreak [16]. This is accompanied by severe declines in individual survival rates and population growth rates, leading to regional-scale decline in population size of more than 90% [22], as well as collapse of age structure [23,24]. At WPP, disease prevalence remained low (less than 20% in adults; less than 10% in juveniles), there was no population decline, and age structure remained unaltered for up to 4 years following the outbreak [20].…”