Loss of speciation rate will impoverish future diversity

Abstract

Human activities have greatly reduced the amount of the earth's area available to wild species. As the area they have left declines, so will their rates of speciation. This loss of speciation will occur for two reasons: species with larger geographical ranges speciate faster; and loss of area drives up extinction rates, thus reducing the number of species available for speciation. Theory predicts steady states in species diversity, and fossils suggest that these have typified life for most of the past 500 million years. Modern and fossil evidence indicates that, at the scale of the whole earth and its major biogeographical provinces, those steady states respond linearly, or nearly so, to available area. Hence, a loss of x% of area will produce a loss of about x% of species. Local samples of habitats merely echo the diversity available in the whole province of which they are a part. So, conservation tactics that rely on remnant patches to preserve diversity cannot succeed for long. Instead, diversity will decay to a depauperate steady state in two phases. The first will involve deterministic extinctions, reflecting the loss of all areas in which a species can ordinarily sustain its demographics. The second will be stochastic, reflecting accidents brought on by global warming, new diseases, and commingling the species of the separate bio-provinces. A new kind of conservation effort, reconciliation ecology, can avoid this decay. Reconciliation ecology discovers how to modify and diversify anthropogenic habitats so that they harbor a wide variety of species. It develops management techniques that allow humans to share their geographical range with wild species.

Adaptive Dynamics and Evolving Biodiversity

“…These antagonistic effects cause the model's biodiversity to peak at a medium environmental quality. Also this prediction is in accordance with observed productivity-diversity relations (Rosenzweig 1995).…”

“…Species diversity tends to increase with the size of the area over which diversity is sampled, a characteristic relationship that is often described by power laws (Rosenzweig 1995). It is therefore noteworthy that the speciation mechanism highlighted by Dieckmann (2003, 2004) also lets the emerging number of species increase with the total area covered by the environmental gradient.…”

“…Reduced speciation rates. Biogeography theory suggests that speciation rates correlate with area (e.g., Rosenzweig 1995Rosenzweig , 2001Losos 1996;Losos and Schluter 2000). Therefore even the largest protected areas and nature reserves may prove far too small to support the speciation of large vertebrates.…”

Niche conservatism above the species level

“…The trajectory of future change is toward conditions-both climatic and otherwise-that species have not experienced in their existence (43). Ongoing habitat degradation, population loss, and human population growth (44,45) may signify an altered continental state such that the North American species pool will contain fewer species overall (45,46), and both environmental change and species loss may occur at rates too fast for species interactions, dispersal, and competitive release to compensate (47). Our results also indicate that perhaps the best and most tractable predictor of mammal response to environmental change lies at the genus level (as a convenient clade for representing deeper evolutionary units).…”

Effect of habitat area and isolation on fragmented animal populations

“…Error bars show 95% confidence intervals. matrix attributes should greatly increase our ability to predict and enhance species' persistence probabilities in fragmented systems (33)(34)(35)(36). Identification of key features that determine whether a species will occupy an area should also improve both occupancy modeling and habitat restoration efforts.…”