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Testing the island effect on phenotypic diversification: insights from the Hemidactylus geckos of the Socotra Archipelago.

Garcia-Porta J, Šmíd J, Sol D, Fasola M, Carranza S - Sci Rep (2016)

Bottom Line: Yet, empirical evidence suggests that it does not always so.To such purpose, we generated a new molecular phylogeny of the group on which we mapped body size and head proportions.These results, although generally consistent with the notion that islands promote high morphological disparity, reveal at the same time a complex scenario in which different traits may experience different evolutionary patterns in the same mainland-island system and continental groups do not always present low levels of morphological diversification compared to insular groups.

View Article: PubMed Central - PubMed

Affiliation: Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta, 37-49, 08003, Barcelona, Spain.

ABSTRACT
Island colonization is often assumed to trigger extreme levels of phenotypic diversification. Yet, empirical evidence suggests that it does not always so. In this study we test this hypothesis using a completely sampled mainland-island system, the arid clade of Hemidactylus, a group of geckos mainly distributed across Africa, Arabia and the Socotra Archipelago. To such purpose, we generated a new molecular phylogeny of the group on which we mapped body size and head proportions. We then explored whether island and continental taxa shared the same morphospace and differed in their disparities and tempos of evolution. Insular species produced the most extreme sizes of the radiation, involving accelerated rates of evolution and higher disparities compared with most (but not all) of the continental groups. In contrast, head proportions exhibited constant evolutionary rates across the radiation and similar disparities in islands compared with the continent. These results, although generally consistent with the notion that islands promote high morphological disparity, reveal at the same time a complex scenario in which different traits may experience different evolutionary patterns in the same mainland-island system and continental groups do not always present low levels of morphological diversification compared to insular groups.

No MeSH data available.


Map showing the geographic limits of this study.The diameters of the circles are proportional to the species richness of the arid clade of Hemidactylus within each geographic region. The map on the left was generated using ArcGIS 10.3 in WGS84 projection based on a map from Natural Earth (http://www.naturalearthdata.com/). The map on the right was made in Inkscape 0.91 (https://inkscape.org), with the boundaries and topography based on the Shuttle Radar Topography Mission data (http://www2.jpl.nasa.gov/srtm/) (designed by Oona Räisänen). The gecko shown in the figure is Hemidactylus granti (picture by Roberto Sindaco).
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f1: Map showing the geographic limits of this study.The diameters of the circles are proportional to the species richness of the arid clade of Hemidactylus within each geographic region. The map on the left was generated using ArcGIS 10.3 in WGS84 projection based on a map from Natural Earth (http://www.naturalearthdata.com/). The map on the right was made in Inkscape 0.91 (https://inkscape.org), with the boundaries and topography based on the Shuttle Radar Topography Mission data (http://www2.jpl.nasa.gov/srtm/) (designed by Oona Räisänen). The gecko shown in the figure is Hemidactylus granti (picture by Roberto Sindaco).

Mentions: While more studies are needed to address the generality of the island effect on empirical grounds, a major stumbling block is the need of well-sampled phylogenies in both island and continental domains. The present study uses a completely sampled mainland-island system, the so-called arid clade of Hemidactylus geckos14 to test whether the patterns of phenotypic diversification in islands actually differ from those occurring in the continent. The arid clade represents a well-studied monophyletic radiation of 48 species distributed across the arid regions of northeast Africa, the Levant, Arabia, the adjoining areas of southwest Asia and, interestingly for our purposes, also in the Socotra Archipelago1415161718 (Fig. 1). This archipelago is located in the northwestern Indian Ocean and originated as a continental fragment that detached from Arabia around 30 Ma19. It comprises two main islands, Socotra and Abd al Kuri (with areas of 3,625 km2 and 133 km2 respectively) and two small islets, Darsa and Samha (5.4 km2 and 40 km2, respectively), situated 380 km off the southeast coast of Arabia (Yemen), and approximately 100 km east of Somalia off the Horn of Africa (Fig. 1). The Hemidactylus geckos of the arid clade are present on all four islands and have reached the archipelago three times independently, two of them producing subsequent intra-island diversification events1617. Hemidactylus diversity on the small islands of Darsa and Samha is restricted to a single species (H. homoeolepis) also present on Socotra1618.


Testing the island effect on phenotypic diversification: insights from the Hemidactylus geckos of the Socotra Archipelago.

Garcia-Porta J, Šmíd J, Sol D, Fasola M, Carranza S - Sci Rep (2016)

Map showing the geographic limits of this study.The diameters of the circles are proportional to the species richness of the arid clade of Hemidactylus within each geographic region. The map on the left was generated using ArcGIS 10.3 in WGS84 projection based on a map from Natural Earth (http://www.naturalearthdata.com/). The map on the right was made in Inkscape 0.91 (https://inkscape.org), with the boundaries and topography based on the Shuttle Radar Topography Mission data (http://www2.jpl.nasa.gov/srtm/) (designed by Oona Räisänen). The gecko shown in the figure is Hemidactylus granti (picture by Roberto Sindaco).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4829864&req=5

f1: Map showing the geographic limits of this study.The diameters of the circles are proportional to the species richness of the arid clade of Hemidactylus within each geographic region. The map on the left was generated using ArcGIS 10.3 in WGS84 projection based on a map from Natural Earth (http://www.naturalearthdata.com/). The map on the right was made in Inkscape 0.91 (https://inkscape.org), with the boundaries and topography based on the Shuttle Radar Topography Mission data (http://www2.jpl.nasa.gov/srtm/) (designed by Oona Räisänen). The gecko shown in the figure is Hemidactylus granti (picture by Roberto Sindaco).
Mentions: While more studies are needed to address the generality of the island effect on empirical grounds, a major stumbling block is the need of well-sampled phylogenies in both island and continental domains. The present study uses a completely sampled mainland-island system, the so-called arid clade of Hemidactylus geckos14 to test whether the patterns of phenotypic diversification in islands actually differ from those occurring in the continent. The arid clade represents a well-studied monophyletic radiation of 48 species distributed across the arid regions of northeast Africa, the Levant, Arabia, the adjoining areas of southwest Asia and, interestingly for our purposes, also in the Socotra Archipelago1415161718 (Fig. 1). This archipelago is located in the northwestern Indian Ocean and originated as a continental fragment that detached from Arabia around 30 Ma19. It comprises two main islands, Socotra and Abd al Kuri (with areas of 3,625 km2 and 133 km2 respectively) and two small islets, Darsa and Samha (5.4 km2 and 40 km2, respectively), situated 380 km off the southeast coast of Arabia (Yemen), and approximately 100 km east of Somalia off the Horn of Africa (Fig. 1). The Hemidactylus geckos of the arid clade are present on all four islands and have reached the archipelago three times independently, two of them producing subsequent intra-island diversification events1617. Hemidactylus diversity on the small islands of Darsa and Samha is restricted to a single species (H. homoeolepis) also present on Socotra1618.

Bottom Line: Yet, empirical evidence suggests that it does not always so.To such purpose, we generated a new molecular phylogeny of the group on which we mapped body size and head proportions.These results, although generally consistent with the notion that islands promote high morphological disparity, reveal at the same time a complex scenario in which different traits may experience different evolutionary patterns in the same mainland-island system and continental groups do not always present low levels of morphological diversification compared to insular groups.

View Article: PubMed Central - PubMed

Affiliation: Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta, 37-49, 08003, Barcelona, Spain.

ABSTRACT
Island colonization is often assumed to trigger extreme levels of phenotypic diversification. Yet, empirical evidence suggests that it does not always so. In this study we test this hypothesis using a completely sampled mainland-island system, the arid clade of Hemidactylus, a group of geckos mainly distributed across Africa, Arabia and the Socotra Archipelago. To such purpose, we generated a new molecular phylogeny of the group on which we mapped body size and head proportions. We then explored whether island and continental taxa shared the same morphospace and differed in their disparities and tempos of evolution. Insular species produced the most extreme sizes of the radiation, involving accelerated rates of evolution and higher disparities compared with most (but not all) of the continental groups. In contrast, head proportions exhibited constant evolutionary rates across the radiation and similar disparities in islands compared with the continent. These results, although generally consistent with the notion that islands promote high morphological disparity, reveal at the same time a complex scenario in which different traits may experience different evolutionary patterns in the same mainland-island system and continental groups do not always present low levels of morphological diversification compared to insular groups.

No MeSH data available.