Biodiversity Dynamics on Islands: Explicitly Accounting for Causality in Mechanistic Models

Abstract

Island biogeography remains a popular topic in ecology and has gained renewed interest due to recent theoretical development. As experimental investigation of the theory is difficult to carry out, mechanistic simulation models provide useful alternatives. Several eco-evolutionary mechanisms have been identified to affect island biodiversity, but integrating more than a few of these processes into models remains a challenge. To get an overview of what processes mechanistic island models have integrated so far and what conclusions they came to, we conducted an exhaustive literature review of studies featuring island-specific mechanistic models. This was done using an extensive systematic literature search with subsequent manual filtering. We obtained a list of 28 studies containing mechanistic island models, out of 647 total hits. Mechanistic island models differ greatly in their integrated processes and computational structure. Their individual findings range from theoretical (such as humped-shaped extinction rates for oceanic islands) to system-specific dynamics (e.g., equilibrium and non-equilibrium dynamics for Galápagos' birds). However, most models so far only integrate theories and processes pair-wise, while focusing on hypothetical systems. Trophic interactions and explicit micro-evolution are largely underrepresented in models. We expect future models to continue integrating processes, thus promoting the full appraisal of biodiversity dynamics.

Assessing predicted isolation effects from the general dynamic model of island biogeography with an eco‐evolutionary model for plants

“…This is an advantage over spatially implicit, neutral approaches, which often constrain species carrying capacity via an imposed parameter for the maximum number of individuals or species (e.g. in Borregaard et al, ) and without considering individual traits (Leidinger & Cabral, ).…”

“…Moreover, intra‐archipelagic isolation may play an important role for trends of single‐island endemics (Borregaard et al, ; Cabral et al, ), and thus, further insights might be gained by disentangling isolation in relation to intra‐archipelagic versus mainland source pools. Inter‐island dispersal within archipelagos has rarely been considered (Leidinger & Cabral, ), but we anticipate that its explicit consideration should contribute to earlier colonization in young islands and associated decrease in single‐island endemism for older islands (Borregaard et al, ; Whittaker et al, ). Extending integrative process‐based frameworks, such as ours, to include archipelagic dynamics should enable scrutiny of inter‐island isolation dynamics, opening ground for theoretical developments and conservation assessments (e.g.…”

Interactions between ecological, evolutionary and environmental processes unveil complex dynamics of insular plant diversity

“…Hence, typical biogeographical processes (e.g. colonization and extinction) become emergent rather than imposed (Leidinger & Cabral, ). This provides insights across ecological levels (Harfoot et al, ; Rosindell & Harmon, ; Urban et al, ) and integrates ecological and biogeographical theories by linking low‐ with high‐level processes (Cabral et al, ; Leidinger & Cabral, ).…”

“…Pattern‐oriented models distinguish the effects of different combinations of parameter values that generate similar patterns at a given scale by evaluating patterns at other scales. For this, low‐level models are ideal because they generate patterns at multiple ecological levels (Cabral et al, ; Leidinger & Cabral, ). Likewise, a useful study system should be simple, but still informative across different scales and ecological levels, such as oceanic islands (Leidinger & Cabral, ; Losos & Ricklefs, ; Warren et al, ).…”

Plant diversity in Oceanic archipelagos: realistic patterns emulated by an agent‐based computer simulation

“…For instance, according to Leidinger's and Cabral's (2017) analyses, most island models have dealt with hypothetical single island -mainland systems; examining real-world islands (Hortal et al 2009, Rosindell and Phillimore 2011, Avery et al 2013, Valente et al 2015 or archipelago systems (Durrett and Levin 1996, Birand and Howard 2008, Warren 2010, Yamaguchi and Iwasa 2017 have both been rather rare. These simplifications may be necessary to realize fundamental processes, although they can rarely answer specific questions requiring more complex simulations (Leidinger and Cabral 2017). Most island models to date have been neutral, i.e.…”