Ecological specialization, rather than the island rule, explains morphological diversification in an ancient radiation of geckos

Island colonists are often assumed to experience higher levels of phenotypic diversification than their continental sister taxa. However, empirical evidence shows that exceptions to the familiar "island rule" do exist. In this study, we tested this rule using a nearly complete sampled mainland-island system, the genus Pristurus, a group of sphaerodactylid geckos mainly distributed across continental Arabia and Africa and the Socotra Archipelago. We used a recently published phylogeny and an extensive dataset of morphological measures to explore whether island and mainland taxa share the same morphospace or if they present different dynamics of phenotypic evolution. Moreover, we used habitat data to examine if ecological specialization is correlated with morphological change, reconstructing the ancestral habitat states across the phylogeny to compare the level of phenotypic disparity and trait evolution between habitats. We found that insular species do not present higher levels or rates of morphological diversification than continental groups. Instead, habitat specialization provides insight into the evolution of body size and shape in Pristurus. In particular, the adaptation to exploit ground habitats seems to have been the main driver of morphological change, producing the highest levels of disparity and evolutionary rates. Additionally, arboreal species show very constrained body size and head proportions, suggesting morphological convergence driven by habitat specialization. Our results reveal a determinant role of ecological mechanisms in morphological evolution and corroborate the complexity of ecomorphological dynamics in mainland-island systems.

A new species of Hetereleotris (Teleostei: Gobiidae) from the Socotra Archipelago (north-western Indian Ocean), a rare case of a hole-associated adaptation in gobiid fishes

A new cryptobenthic gobiid species Hetereleotris nasoramosa sp. nov. is described based on the holotype and five paratypes collected from the north-eastern part of Socotra Island, Arabian Sea, from moderately large pieces of coral rocks with holes at depths of 8–11 m. Molecular phylogenetic analysis placed the new species within the genus Hetereleotris. Hetereleotris nasoramosa sp. nov., differs from all species of Hetereleotris in having developed tentacles extending from each anterior and posterior nostril and five transverse suborbital papillae rows (instead four or six in other species). The new species superficially resembles the recently described Red Sea endemic species Cerogobius petrophilus by having forward-set, elevated eyes, a short snout, a moderately large mouth, a relatively deep and short caudal peduncle, and developed tentacles on the head, but differs from it by the same characters of developed tentacles extending from each anterior and posterior nostril and five transverse suborbital papillae rows as from other Hetereleotris species. Both species also share a specific habitat preference for tight holes in rock covered by micro-algae. A full description of the species is provided as well as a revised key to the species of Hetereleotris.

Flying fishes (Beloniformes: Exocoetidae) of the Socotra Archipelago with comments on status of Exocoetus socotranus Steindachner

A checklist of the flying fishes found in the waters off Socotra Archipelago, northwestern part of the Indian Ocean, is provided based on published and original data. Thirteen species from five genera occur in the study area, and four more species found nearby. Keys for the species identification are provided. The type specimen of Exocoetus socotranus Steindachner, 1902 was examined and is determined to be a junior synonym of Cypselurus naresii (Günther, 1889).

Correction to: Dragonfies of Dragon’s Blood Island: Atlas of the Odonata of the Socotra Archipelago (Yemen)

A correction to this paper has been published: https://doi.org/10.1007/s12210-021-01006-z

A new thermosbaenacean of the genus Tethysbaena (Peracarida, Thermosbaenacea, Monodellidae) from Socotra Island, Yemen

A new species of the thermosbaenacean genus Tethysbaena Wagner, 1994 (Crustacea: Peracarida: Thermosbaenacea) is described based on females from a freshwater cave lake and a brackish coastal well on Socotra Island (Yemen) as Tethysbaena dioscorida n. sp. It is the first representative of the Thermosbaenacea that is described from the Socotra Archipelago and the first member of the order known from an Indian Ocean island. The new species is the eighth known member of what is considered the “Tethysbaena relicta” species-group, which is known from Oman (four species), Somalia (one species), Israel (two species) and now Socotra Island (one species). The new species shows closest morphological affinities with T. barbatula Wagner, 2020 from Oman. We suggest that the speciation in this well-defined species-group is due to regressions of the Tethys Sea and the appearance of dry land since the Oligocene-Miocene boundary to the present time, forming major barriers and creating isolated populations of the ancestral species. Also the potential biocrisis in Socotra as a result of developmental activities during the last decades is mentioned, which may affect the subterranean faunas in particular in coastal areas, exemplified by the destruction of one of only two localities where the new species was found.

Notes on batoid fishes of the Socotra Archipelago (north-western Indian Ocean), with four new records

The species composition of batoid fishes from coastal waters of the Socotra Archipelago is reviewed, with confirmed records of the wedgefish Rhynchobatus djiddensis (Forsskål, 1775) and four new records of sharkrays, wedgefishes, and guitarfishes based on collected specimens, including one species from Abd al-Kuri Island, Rhina ancylostoma Bloch & Schneider, 1801 (Rhinidae), and three species from the main island Socotra, Acroteriobatus salalah (Randall & Compagno, 1995) and Rhinobatos punctifer Compagno & Randall, 1987 (Rhinobatidae), and Rhynchobatus australiae Whitley, 1939 (Rhinidae). Among the new records for the Socotra Archipelago, R. australiae represents the first verified record for the Arabian region. In addition, records of four stingray species (Dasyatidae) are verified based on underwater observations accompanied with photographs. All recorded batoid fishes are commercial species caught in the local small-scale fishery. Information on the identification and distribution of each species is provided.

Exploring the historical distribution of Dracaena cinnabari using ethnobotanical knowledge on Socotra Island, Yemen

Background In this study, we present and analyze toponyms referring to Socotra Island’s endemic dragon’s blood tree (Dracaena cinnabari) in four areas on the Socotra Archipelago UNESCO World Heritage site (Republic of Yemen). The motivation is the understanding of the past distribution of D. cinnabari trees which is an important part of conservation efforts by using ethnobotanical data. We assumed that dragon’s blood trees had a wider distribution on Socotra Island in the past. Methods This research was based on field surveys and interviews with the indigenous people. The place names (toponyms) were recorded in both Arabic and the indigenous Socotri language. We grouped all toponyms into five different categories according to the main descriptor: terrain, human, plant, water, and NA (unknown). Also, this study identified current and historical Arabic names of dragon’s blood trees of the genus Dracaena through literature review. Results A total of 301 toponyms were recorded from the four study areas in Socotra Island. Among names related to plants, we could attribute toponyms to nine different plants species, of which six toponyms referred to the D. cinnabari tree, representing 14.63% of the total phytotoponyms in the category. Three historical naming periods prior to 2000 could be identified. The most commonly used name for dragon’s blood trees (D. cinnabari, D. serrulata, D. ombet) appears to be “ahrieb” “إعريهب” and its resin “dum al-akhawin” “دم الأخوين,” while derived (mixed-cooked) products are called “eda’a” “إيدع,” while regionally different names can be found. Conclusion The place names that refer to D. cinnabari are herein suggested to represent remnant areas of once large populations. Therefore, the toponyms may support known hypotheses based on climate models that D. cinnabari had a wider distribution on Socotra Island in the past. This study also confirmed the historical importance of dragon’s blood.

The topology of a plant-insect visitation network from the Hajar Mountains, Oman

The Arabian Peninsula is a hotspot for bee diversity but studies looking at plant-insect interactions there remain rare. A network analysis of insects visiting wildflowers in the Hajar Mountains, Oman was made from the results of eight survey periods between 2016 and 2020. Centrality scores were used to assess the role different groups of potential pollinators play in network topology. A list of 113 insect species visiting 26 plant species has been compiled with Lepidopteran species acting as important connectors within the network. A nested, asymmetric and compartmentalised network was recorded. The order Hymenoptera was the most species rich group, with 46 species recorded followed by Diptera (43 spp.), Lepidoptera (13 spp.), and Coleoptera (11 spp.). Amegilla pyramidalis (Kirby, 1900) (Hymenoptera: Apidae: Antho phorini) is recorded for the first time outside of the Socotra Archipelago. The study is the first specific effort to record the flower visitation behaviour of insects in Oman and gives an overview of the resulting visitation network.

Exploring the historical distribution of Dracaena cinnabari using ethnobotanical knowledge on Socotra Island, Yemen

BackgroundIn this study, we present and analyze toponyms referring to Socotra Island’s endemic dragon’s blood tree (Dracaena cinnabari) in four areas of the Socotra Archipelago UNESCO World Heritage site (Republic of Yemen). The motivation is understanding of the past distribution of D. cinnabari trees which is an important part of conservation efforts by using ethnobotanical data. We assumed that dragon’s blood trees had a wider distribution on Socotra Island in the past. MethodsThis research was based on field surveys and interviews with the indigenous people. The place names (toponyms) were recorded in both, Arabic and indigenous Socotri language. We grouped all toponyms into five different categories according to the main descriptor: Terrain, Human, Plant, Water and NA (unknown). In addition, this study identified current and historical Arabic names of dragon’s blood trees of the genus Dracaena, through literature review. ResultsA total of 301 toponyms were recorded from the four study areas in Socotra Island. Among names related to plants, we could attribute toponyms to nine different plant species, of which six names referred to the D. cinnabari tree, representing 14.63% of total phytotoponyms in the category. Three historical naming periods prior to 2000 could be identified. The most commonly used Arabic name for dragon’s blood trees (D. cinnabari, D. serrulata. D. ombet) appears to be “ahrieb” "إعريهب", its resin “dum al-akhawin” “دم الأخوين”, while derived (mixed-cooked) products are called “edah” “إيدع”; while regionally different names can be found.ConclusionThe place names that refer to D. cinnabari are herein suggested to represent remnant areas of once large populations. The toponyms may therefore support known hypotheses based on climate models that D. cinnabari had a wider distribution on Socotra Island in the past. This study also confirmed the historical importance of dragon’s blood