The value of considering demographic contributions to connectivity: a review

Abstract

Connectivity is a central concept in ecology, wildlife management, and conservation science. Understanding the role of connectivity in determining species persistence is increasingly important in the face of escalating anthropogenic impacts on climate and habitat. These connectivity augmenting processes can severely impact species distributions and community and ecosystem functioning. One general definition of connectivity is that it is an emergent process arising from a set of spatial interdependencies between individuals or populations, and increasingly realistic representations of connectivity are being sought. Generally, connectivity consists of a structural component, relating to the distribution of suitable and unsuitable habitat, and a functional component, relating to movement behavior, yet the interaction of both components often better describes ecological processes. Additionally, although implied by ‘movement', demographic measures such as the occurrence or abundance of organisms are regularly overlooked when quantifying connectivity. Integrating such demographic contributions based on the knowledge of species distribution patterns is critical to understanding the dynamics of spatially structured populations. Demographically‐informed connectivity draws from fundamental concepts in metapopulation ecology while maintaining important conceptual developments from landscape ecology, and the methodological development of spatially‐explicit hierarchical statistical models that have the potential to overcome modeling and data challenges. Together, this offers a promising framework for developing ecologically realistic connectivity metrics. This review synthesizes existing approaches for quantifying connectivity and advocates for demographically‐informed connectivity as a general framework for addressing current problems across ecological fields reliant on connectivity‐driven processes such as population ecology, conservation biology and landscape ecology. Using supporting simulations to highlight the consequences of commonly made assumptions that overlook important demographic contributions, we show that even small amounts of demographic information can greatly improve model performance. Ultimately, we argue demographic measures are central to extending the concept of connectivity and resolves long‐standing challenges associated with accurately quantifying the influence of connectivity on fundamental ecological processes.

Dynamic habitat suitability and connectivity analyses to inform management of an invasive species and conservation of its native competitor

“…We veri ed that previous studies obtained similar home ranges Zabala et al 2007;Fournier et al 2008;Harrington and Macdonald 2008;Peters et al 2009;Zschille et al 2012;Palomares et al 2017;Halbrook and Petach 2018). Lastly, we used the area of these habitat patches to estimate species abundance assuming a proportional relationship to patch size (Drake et al 2021). Aside from the ten sets of habitat patches for each species (one per period and scenario), we calculated the overall potential habitat by aggregating the habitat patches of all periods and scenarios to represent the total area that could be colonized at any time by each species.…”

Spatiotemporal connectivity dynamics in spatially structured populations

“…In our case, relative support for the relaxation of specific assumptions suggests that demographic weighting was more important than allowing for temporally varying dispersal (Table 1). This outcome is notable as the assumptions being relaxed in this study represent those often violated, out of necessity or convenience, in many studies (Drake et al, 2021). In particular, and for example, water voles experience frequent turnover events, limiting the pool of dispersers and introducing false positives in structural measures.…”

“…We add empirical weight to the theoretical assertion that it is important to consider connectivity dynamics as an inherent property of any spatially-structured landscape (Zeller et al, 2020). And critically, we highlight the fundamental, but often overlooked, role of demography as a major contributor to connectivity dynamics (Drake et al, 2021).…”

“…of connectivity modelling assumptions reflects increasing realism of connectivity estimated from occupancy data with focus on demographic contributions and helps account for shifts in dispersers (Drake et al, 2021). We refer to these as unweighted with timeinvariant dispersal (UI), demographically weighted with time-invariant dispersal (DI), unweighted with time-varying dispersal (UV) and demographically weighted with time-varying dispersal (DV).…”

Asymmetrical gene flow between coastal and inland dunes in a threatened digger wasp

“…We hence hypothesize that the establishment of new populations may only succeed when Allee-effects are overcome by the simultaneous settlement of multiple females into a single cluster. Such demographic contributions are often overlooked in the dynamics of spatially structured populations in both population genetics and connectivity studies (Lowe et al 2017; Drake et al 2022). We indeed found that the few new populations included in our study originate from other large (meta)populations: at the coast from the western coastal area and inland from a mixture of coastal populations and the one nearby old, large inland population (Geel-Bel, 46).…”