Life-history variation among populations of Canadian Toads in Alberta, Canada

Abstract

Development of appropriate conservation plans relies on life-history information and how life-history traits vary across populations of a species. Such data are lacking for many amphibians, including the Canadian Toad (Bufo hemiophrys Cope, 1886). Here we use skeletochronology to estimate size at age, growth rates, age at maturity, and longevity of toads from nine populations along a latitudinal gradient in Alberta, Canada. Size of individual toads within each year class was highly variable, but age and size (measured as snout-to-urostyle length) were significantly related for almost all populations. The largest individuals were found in the southern-most population, while the smallest toads were found in three populations from the middle of the latitudinal range studied. Growth rates were highest in the southern-most population and lowest at the three populations with relatively small individuals. Maximum age was from 7 to 12 years for the populations sampled. The oldest individuals were found in populations in the middle of the latitudinal range sampled; toads in these populations were smaller than those in all other populations. Age at maturity was 1 year old for males and 2 years old for females in most populations. This study shows that some life-history traits exhibit significant variation between Canadian Toad populations, suggesting that effective conservation of this species will need to include population or area-specific management.

The pitfalls of extrapolation in conservation: movements and habitat use of a threatened toad are different in the boreal forest

“…However, if northern B. hemiophrys use different kinds of habitats from conspecifics elsewhere in the range, that understanding will not come from the published literature, but only from site-specific study. Recent work has shown significant geographic variation in life-history characteristics of B. hemiophrys (Eaton et al, 2005). In this study, we test whether there is also geographic variation in movement ecology and habitat use of this species that is pertinent to its conservation and management.…”

“…For example, wide-ranging species may exhibit substantial geographic variation in life-history traits (e.g. Fleming & Gross, 1990;Ritke, 1990;Gregory & Larsen, 1993;Eaton et al, 2005), which will reflect potential differences in population dynamics and responses to disturbance. When other aspects of a species' ecology, such as habitat use and seasonal movement patterns, also vary geographically, the application of data from one region to another will be even more counter-productive.…”

Adult body size = f (initial size + growth rate × age): explaining the proximate cause of Bergman’s cline in a toad along altitudinal gradients

“…(1) Two distinct size patterns along latitudinal or altitudinal gradients have been identified among anuran species (review in Ashton 2002): some conform to Bergmann's rule (e.g. Leclair and Laurin 1996;Lai et al 2005;Lu et al 2006;Ma et al 2009a;Liao and Lu 2010a;Gillespie 2011), whereas others do the opposite (Ryser 1996;Eaton et al 2005;Matthews and Miaud 2007;Cvetković et al 2009;Ma et al 2009b;Sinsch et al 2010). This offers opportunities to assess relative roles of the size-related parameters in shaping the direction and degree of geographic size clines.…”

Rapid decline and extinction of a montane frog population in southern Australia follows detection of the amphibian pathogen Batrachochytrium dendrobatidis

“…Diagnosing population declines can be difficult because multiple factors may be involved and population demographic data are often inadequate (Biek et al, 2002;Blaustein & Kiesecker, 2002;Eaton et al, 2005). Identifying the relative impact and context-specific interactions among different threatening processes is critical to understanding population declines (Blaustein & Kiesecker, 2002;Collins & Storfor, 2003;Blaustein et al, 2011).…”