frontiers of geobiology

Key Concepts in Geoecodynamics

As an interdisciplinary science, Geoecodynamics incorporates  concepts from many sciences. Two new complementary concepts are key to exploit the genomic record in practice, as they explain how genomic variation is organized at the tiers of the population-species and ecosystem-landscape. These concepts focus on how species can be studied as biotic indicators of the landscape in which they have evolved.

One is the Phylogeographic Record. It conceptualizes the species’ tenure in its habitat as a life history through which demographic processes have shaped an envelope of genomic variation. Two, the concept of the Palaeoplex operationalizes the Phylogeographic Record, using sequence data of selected DNA markers as proxies of the total genomic variation of the species. Palaeoplex include all the statistics used in phylogeography and phylogenetic systematics, such as estimates of divergence dates of lineages. These twinned concepts account for the ontological and operational aspects, respectively, of the Genomic Record of Earth history.

This dichotomy between the phylogeographic record and palaeoplex of an evolving populational lineages is directly analogous to the distinction between the non-operational species concept (ESC) in its ontological primacy, and different species criteria (also called operational species concepts) used to discover the existence of species. These species-specific proxies derived from the genomic record enable us to quantify evolutionary events in species’ evolution. Focusing on regional to local spatio-temporal scales of landscape evolution, these twinned concepts of the Phylogeographic Record and Palaeoplex the researcher to realize the potentials of geoecodynamics, and study biodiversity dynamics as an earth surface process.

In turn, the individual events we recover using genomic evidence in a species’ evolution are the proxies, with which we can constrain the tenures of discrete landforms – and other aspects of palaeoenvironments – in the evolving landscape. Among the insights we can glean into turnovers of species are derived from focusing on births and deaths and other major demographic events in the tenures of species. Contingent on habitat fidelity, these proxies can be linked to the habitats (Ecospace) and in turn individual landforms (Geospace) within which biodiversity dynamics have tracked formative events in evolving landscapes (their landforms and palaeoenvironments). Ecological specialists – stenotopes – are ideal biotic indicators, because these species are more tightly confined by the local ecophysiological conditions of respective habitat patches. In short, stenotopes exhibit high fidelity to individual landforms.

Habitats comprise the Ecospace matrix inhabited by evolving biota, which are hosted in the Geospace: the landforms comprising the evolving landscape. Aquatic species dependent on wetlands, and troglobitic species in caves are superb examples of stenotopes whose evolution has been locked into specific landforms; these tighter niche constraints contain the spatial demographics of such species, and in has acted to increase their sensitivity to events that modify the landscape. More formally, it links the vibrant research area of niche modelling, in ecology, directly into geoecodynamics; albeit geoecodynamics recasts focuses on the dynamics of genomic variation of species respective to their niches in evolving landscapes.

This brief kinematic overview of geoecodynamics presented above is obviously scale-free. We can exploit key categories ‘landform’, ‘species’ and ‘niche’, and study different suites of evolving individuals making up a landscape in a geobiological framework. We can reconstruct how the interplay between the biota and the landscape has played out over evolutionary scales. The specifics of demographic processes in the different species have been shaped in the landscape mosaic through the matrix of habitat space under a changing environment. This perspective underpinning geoecodynamics underscores that landscape space – the geospace – is inherently dynamic, because the patch mosaic of landforms has evolved in response to the interplay of earth surface processes under ultimate control of the evolving earth system.

The spatio-temporal domains containing biotic dynamics are not only complex but they are also diverse. These make for fortuitous circumstances for Geoecodynamics. The extant biodiversity presents the investigator with no shortage of biotic indicators of landscape dynamics. One of the most exciting arenas of this new approach lies in testing how far – and where – we can explore these dynamics, and map out their corresponding patterns of genomic variation shaped within the individuated histories of complex dynamic landscapes.

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