Functional endemism: population connectivity, shifting baselines, and the scale of human experience

Abstract

Quantifying population connectivity is important for visualizing the spatial and temporal scales that conservation measures act upon. Traditionally, migration based on genetic data has been reported in migrants per generation. However, the temporal scales over which this migration may occur do not necessarily accommodate the scales over which human perturbations occur, leaving the potential for a disconnect between population genetic data and conservation action based on those data. Here, we present a new metric called the “Rule of Memory”, which helps conservation practitioners to interpret “migrants per generation” in the context both of human modified ecosystems and the cultural memory of those doing the modification. Our rule states that clades should be considered functionally endemic regardless of their actual taxonomic designation if the migration between locations is insufficient to maintain a viable population over the timescales of one human generation (20 years). Since larger animals are more likely to be remembered, we quantify the relationship between migrants per human (N) and body mass of the organism in question (M) with the formula N = 10M−1. We then use the coral reef fish Pomacentrus moluccensis to demonstrate the taxonomic and spatial scales over which this rule can be applied. Going beyond minimum viable population literature, this metric assesses the probability that a clade's existence will be forgotten by people throughout its range during a period of extirpation. Because conservation plans are predicated on having well-established baselines, a loss of a species over the range of one human generation evokes the likelihood of that species no longer being recognized as a member of an ecosystem, and thus being excluded in restoration or conservation prioritization. [Correction added on 26 December 2012, after first online publication: this formula has been corrected to N=10M−1].

First record of the North African Launaea arborescens in southern Africa

“…The extent and size of the population contribute to determining whether a population can be considered self-sustaining and therefore viable. Isolated individuals of a species far from other individuals of the same species can hardly present a viable population, particularly if these are out-crossers and therefore rely on genetic exchange with other individuals (Harper 1977;Drew & Kaufman 2013). The size distribution of the plants provides an indication of the population status (Figure 4).…”

Culturally transmitted song exchange between humpback whales ( Megaptera novaeangliae ) in the southeast Atlantic and southwest Indian Ocean basins

“…While the fields of genetics and more recently genomics [10] have proved invaluable for understanding population structure and connectivity of marine mammals over historical time scales, limitations exist for interpreting contemporary movement and connectivity patterns using these methods. Using additional methods that can contribute behavioural and/or environmental information at a higher temporal resolution can prove beneficial for informing conservation and management decisions [11].…”

Learning and Behavior in Reef Fish: Fuel for Microevolutionary Change?

“…In our piece, we aim to use the fascinating observational and experimental work performed by Wismer et al as an entry point into how learned behaviors could potentially join biogeography and behavior as mechanisms explaining the observed diversity of reef fish population structure. Over the past 15 yr, a body of work has emerged suggesting that marine species which were previously considered geographically widespread are actually groups of closely related and range restricted species (Terry et al 2000;Colborn et al 2001;Taylor & Hellberg 2005;Drew et al 2008Drew et al , 2010DiBattista et al 2011DiBattista et al , 2012Drew & Kaufman 2012;Liu et al 2012;Bernardi 2013). We now know that the evolutionary mosaic of marine species is much more finely partitioned and that factors such as local ecological conditions can play a major role in the evolutionary history of fishes (Rocha et al 2005;Dawson 2012).…”