Species Migrationary Response to Climate Change - A Poster

Below is the poster created from the work already put forward by this blog. An innovative design breathes fresh life into academic posters that can sometimes be very much alike.

Glacial Refugia - Are They Being too Cryptic?

As previously promised, todays post will be discussing glacial refugia. During the Last Glacial Maximum at around 23,000 to 18,000 BP most of the temperate biota existed in lower latitude refugia. Extensive analysis has revealed the existence of three main refugia in the Mediterranean peninsulas of Iberia, Italy and the Balkans. After the LGM, Europe was recolonized from these refugia by species migrating northwards. However using phylogeographical evidence, the possibility of cryptic altitudinal refugia has arisen (Provan & Bennett 2008). This may have led to gross overestimations of species dispersal capabilities, which could in turn cause problems for estimations of species migrations in the future.

Phylogeographic techniques involve exploring species diversity as an indicator for possible refugia. Species that have survived the glacial maxima in refugia will expect to have high levels of genetic diversity. Secondly long term isolation of populations will lead distinct genetic lineages and lead to possible recolonization routes which can then be used to locate refugia. Areas with high genetic diversity that have been recolonized by many separate refugia might lead to confusion and should therefore be taken into account. Figure 2 below shows phylogeographic evidence of red seaweed (Palmaria palmata) showing a refugia in the English channel. The different colours represent different genetic types, with the highest proportion being shown in the dotted area.

Figure 2. Distribution of Palmaria palmata in Northern Europe (Provan et al. 2005)

Although phylogeographic evidence has had success locating recolonization pathways, it does not explain population dynamics during phases of species contraction. It is unclear whether species migrate to refugia during changes in climate or simply species outside the refugia become extinct. Studies of the Artic fox (Alopex lagopus) using ancient DNA data techniques have established that during post glacial contraction species outside the refugia became extinct (Dalen et al. 2007). This might have a massive effect on cold-adapted species that contract during periods of warming.

Phylogeographic techniques has provided new insights into the locations of glacial refugia. They have challenged the theory that the southern refugia were the only source of recolonization for temperate species after the LGM. The identification of cyrptic refugia has important implications for future climate change due to estimations of species migration range.

The Bioclimate Envelope - Outdated and Simple?

Todays post will focus on the bioclimate envelope model and discuss whether they are useful in determining species migrationary response to climate change. The bioclimate envelope model has its roots in the ecological niche theory. The ecological niche is a conceptual space comprising all of the environmental variables in which a species can survive and grow. The bioclimate envelope can be defined as the climatic component of the ecological niche. Therefore it involves understanding the current species distribution, and how species physiologically will respond to climate change. It might enable us to make a redistribution of species over time using climate models.

The model is widely used in decision making on future climate change, however there are some criticisms. Pearson & Dawson (2003) express concern at how the model does not take into account how species interact with each other, rather how only they function alone. Since ecosystems are a complex web of interactions and feedbacks, taking into account only the species that is being studied could lead to erroneous model predictions. Another possible facet that is not included is evolutionary change. Studies by Thomas et al. (2001) and Woodward (1990) has studied rapid evolutionary change response to climate change of plant and insect species. This involves studying climate induced shifts in species, often excluding phenotypes that are poor dispersers or poorly adapted to local conditions.

Looking forward, the development of dynamic global species models would be a more accurate approach. There has been recent development of models on regional scales that break down ecosystems processes into key components and use that to spatially and temporally model species range shifts. However due to the complexity of these models, application to global scales have not yet been possible. This means that bioclimate envelope models are still perhaps the best available guide for policy making at the present time, though they must be viewed skeptically.