deferred costs

dustinmeeg

Propagule size and dispersal costs mediate establishment success of an invasive species

Authors: Rolanda Lange and Dustin J Marshall

Published in: Ecology, volume 97, issue 3 (March 2016)

Abstract

Bio-invasions depend on the number and frequency of invaders arriving in new habitats. Yet, as is often the case, it is not only quantity that counts, but also quality.

The process of dispersal can change disperser quality and establishment success. Invasions are a form of extra-range dispersal, so that invaders often experience changes in quality through dispersal.

To study effects of dispersal on invader quality, and its interactions with quantity on invasion success, we manipulated both in a field experiment using an invasive marine invertebrate.

Establishment success increased with the number of individuals arriving in a new habitat. Prolonged larval durations – our manipulation of prolonged dispersal – decreased individual quality and establishment success. Groups of invaders with prolonged larval durations contributed only a third of the offspring relative to invaders that settled immediately.

We also found an interaction between the quality and quantity of invaders on individual growth: only within high-quality cohorts did individuals experience density-dependent effects on growth.

Our findings highlight that dispersal not only affects the quantity of invaders arriving in a new habitat but also their quality, and both mediate establishment success.

Citation

Lange R , Marshall DJ (2016) Propagule size and dispersal costs mediate establishment success of an invasive species. Ecology, 97(3), 2016, pp. 569–575
DOI: 10.1890/15-1573 PDF 238 KB

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How do dispersal costs and habitat selection influence realized population connectivity?

Authors: Scott C Burgess, Eric A Treml and Dustin J Marshall

Published in: Ecology, volume 93, issue 6, doi: 10.1890/11-1656.1

Abstract

Despite the importance of dispersal for population connectivity, dispersal is often costly to the individual.

A major impediment to understanding connectivity has been a lack of data combining the movement of individuals and their survival to reproduction in the new habitat (realized connectivity).

Although mortality often occurs during dispersal (an immediate cost), in many organisms costs are paid after dispersal (deferred costs). It is unclear how such deferred costs influence the mismatch between dispersal and realized connectivity.

Through a series of experiments in the field and laboratory, we estimated both direct and indirect deferred costs in a marine bryozoan (Bugula neritina). We then used the empirical data to parameterize a theoretical model in order to formalize predictions about how dispersal costs influence realized connectivity.

Individuals were more likely to colonize poor-quality habitat after prolonged dispersal durations. Individuals that colonized poor-quality habitat performed poorly after colonization because of some property of the habitat (an indirect deferred cost) rather than from prolonged dispersal per se (a direct deferred cost).

Our theoretical model predicted that indirect deferred costs could result in nonlinear mismatches between spatial patterns of potential and realized connectivity.

The deferred costs of dispersal are likely to be crucial for determining how well patterns of dispersal reflect realized connectivity. Ignoring these deferred costs could lead to inaccurate predictions of spatial population dynamics.

Full paper

Burgess SC, Treml EA, Marshall DJ (2012) How do dispersal costs and habitat selection influence realized population connectivity? Ecology 93: 1378–1387 PDFPDF 622 KB doi: 10.1890/11-1656.1