Interacting stressors and the potential for adaptation in a changing world: responses of populations and individuals

Abstract

To accurately predict the impact of environmental change, it is necessary to assay effects of key interacting stressors on vulnerable organisms, and the potential resiliency of their populations. Yet, for the most part, these critical data are missing. We examined the effects of two common abiotic stressors predicted to interact with climate change, salinity and temperature, on the embryonic survival and development of a model freshwater vertebrate, the rough-skinned newt (Taricha granulosa) from different populations. We found that salinity and temperature significantly interacted to affect newt embryonic survival and development, with the negative effects of salinity most pronounced at temperature extremes. We also found significant variation among, and especially within, populations, with different females varying in the performance of their eggs at different salinity-temperature combinations, possibly providing the raw material for future natural selection. Our results highlight the complex nature of predicting responses to climate change in space and time, and provide critical data towards that aim.

Keywords: amphibian; newt; salinity; stress; temperature; variation.

Figure 1.

Life cycle of the rough-skinned newt (T. granulosa). Adults live terrestrially (green background), but return to ponds and streams (blue background) to breed every spring. Mating occurs in the water, followed by the deposition of fertilized eggs on aquatic littoral vegetation. Eggs develop and hatch over the next month, and gilled aquatic larvae grow and develop over the next several months before metamorphosing and returning to land. Photos by G.R.H., B. Gall and A. Spence. Adapted, with permission, from [65].

Figure 2.

Per cent survival in salinity (0, 2, 5 ppt) and temperature (7, 14, 21°C) treatments of eggs from rough-skinned newts (T. granulosa) from four different populations.

Figure 3.

Interfamily variation in per cent survival of eggs from 11 to 12 different female newts (T. granulosa) from each of four different populations in 2 ppt salinity in different temperature treatments (figures showing survival in other salinity treatments can be found in the electronic supplemental material).

Figure 4.

Sublethal effects of salinity and temperature embryonic developmental stress on hatchling newts (T. granulosa) from four different populations. Means ± s.e. (a) Time to hatching (days), (b) length at hatching (mm) and (c) developmental stage at hatching (Harrison stages) [72]. (d) Percentage of offspring born with a developmental deformity.