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Teaser, summary, work performed and final results

Periodic Reporting for period 1 - BetMon (Delivering better fitness estimators for wildlife ecology and management and effective monitoring)

Teaser

Fitness and its traits are used in applied ecology to assess habitat quality and derive scientific knowledge to design and implement management and conservation measures. To assess fitness considering several traits and trade-offs is required, and this is best done with rarely...

Summary

Fitness and its traits are used in applied ecology to assess habitat quality and derive scientific knowledge to design and implement management and conservation measures. To assess fitness considering several traits and trade-offs is required, and this is best done with rarely available multi-years data sets on identified individuals. As a result fitness proxies such as offspring production, whose relationship with actual fitness is poorly understood, are often used. Therefore, many studies, and decisions supported by them, involve unknown biases as a consequence of the knowledge gap in: the relationship between fitness and proxies used, the trade-offs among proxies, and the effect on accuracy of estimations of different proxy/monitoring-effort combinations.
Societal awareness on the management and conservation issues is growing continuously, and in response to it, among other initiatives, many areas have been designed within the Nature2000 network to conserve iconic and keystone species. In order to manage, conserve and communicate the status and trends of wildlife populations knowledge of effective monitoring practices is required.
The original aims included:
1) provide high quality ecological knowledge on the determinant of individual fitness and their trade-offs, and on factors explaining offspring recruitment;
2) assess of the reliability of commonly used fitness proxies; and
3) develop best practice and improvements for short-term monitoring protocols used in research, management and conservation science.

Work performed

1) provide high quality ecological knowledge on the determinant of individual fitness and their trade-offs, and on factors explaining offspring recruitment
Results show weak positive intraindividual covariation among traits related to reproduction and survival, unless under prolonged adverse conditions. Therefore, trade-offs between reproduction and survival were not considered in further analyses.
Trade-offs between brood size and offspring recruitment probability did not impact recruitment in any study species. Recruitment was shaped after brood size and laying date.

2) assess of the reliability of commonly used fitness proxies;
I evaluated individual lambda, lifetime reproductive success (LRS) and several combinations of lifespan proxies and annual-productivity metrics. LRS outperformed all the other in every species, while most of the variation explained by LRS was contributed by the lifespan axis.

3) develop best practice and improvements for short-term monitoring protocols used in research, management and conservation science.

Imodelled LRS estimated through different monitoring periods and sampling sizes (individuals/territories) using MonteCarlo techniques to estimate the minimum detectable change with each monitoring design. This was done for four different species with differnet life-histories to allow manages to estimate the capability of their monitoring design and to refine it to accomplish the desired management/research goal.

In addition the project, or some of the results, were presented in one international conference, two university seminars, and a in a Explorathon (a public outreach event organised by the University of Aberdeen in which researchers present their projects to the broad public and later discuss them with citizens in an informal café environment.

Final results

In order to provide high quality ecological knowledge on the determinant of individual fitness and their trade-offs, and on factors explaining offspring recruitment,
I estimated the contribution of trade-offs to inter-individual variation in life-history traits, opposed to most research on trade-offs focused on their detectability and evolution. I estimated the covariation among the survival and reproduction traits most frequently reported in the literature using top quality, long-term monitoring data of five raptor species. I furthermore accounted for the effects of adverse environmental conditions of three different lengths (1 to 3 years) upon the start of the breeding career and for natal conditions, and used meta-analysis techniques to combine and generalize species-specific results.
I found limited evidence for covariation among fitness-related traits under normal environmental conditions. However under prolonged adverse environmental conditions trade-offs between early reproduction and subsequent reproduction or survival became apparent.
Before the project belief was that trade-offs shape individual life-histories within populations, although how commonly there are expressed and the strength of the relationships remained unknown. After our analyses I realised that trade-offs contribute little to inter-individual variation in trait values over ecological time scales, unless individuals experience prolonged adverse conditions when trade-offs may account for ~4 % of the observed variation in trait-values. These findings also have an applied value as researchers can use them to determine whether in their research scenario it might be unwise to disregard possible contributions of trade-offs to measured traits. For instance when assessing impact of extrinsic factors (e.g. habitat type or management actions) on breeding output in a population that has experienced adverse conditions for a prolonged period, trade-offs are likely and bias results if not accounted for.

Regarding offspring survival and recruitment, I analysed the effect on recruitment of brood size, offspring body condition, their trade-offs, and hatching date. I also accounted for the variation in food availability, weather and other environmental conditions that may create cohort effects. Trade-offs resulted in significant negative correlations between brood size and body condition in two of the four species, but their effect in recruitment were negligible. Body condition of nestlings had no or marginal effect on recruitment probability, even after controlling for interactions with hatching date, post-fledging weather conditions or food conditions. In 3 of the 4 species individuals who produced larger broods size had a higher probability that one or more of their offspring were later recruited some offspring whereas large brood size it did not diminish, or only marginally, individual probability of recruitment. The number of recruits produced per brood was related to brood size and hatching date in three species, and together explained 0.040 (±0.029) of the observed variation in recruitment and accounted for 24 % (±18) of the variation in recruitment explained by fixed factors. On average hatching date was slightly better predictor of recruitment than brood size, as it accounted for more partial variation.


The best proxy for local recruits produced was LRS. I have modelled estimated LRS to show which is the minimum of change a given monitoring design can detect.

Website & more info

More info: http://www.abdn.ac.uk.