Research Article ISSN 2336-9744 (online) | ISSN 2337-0173 (print) The journal is available on line at www.biotaxa.org/em Arachnogeographical comparison between West Palearctic and Afrotropical Areas PETAR BERON National Museum of Natural History, Tsar Osvoboditel Bld 1, 1000 Sofia, Bulgaria e-mail: [email protected] Received 5 September 2016 │ Accepted 25 November 2016 │ Published online 28 November 2016. Abstract Comparison is made between the Arachnofaunas of Western Palearctic (Europe, SW Asia and North Africa to 20oN) and Afrotropical (from 20oN to the line Zambezi – Kunene) areas. This border (actually transition zone) divides two Kingdoms – Holarctic and Paleotropic. What concerns Arachnida so far such comparison has never been made (for all the orders). Outlined are the endemic taxa and it is clear that the difference is due mostly to climatic difference (for the warm preferring groups like Schizomida, Amblypygi, Solifugae, Scorpiones, Ricinulei). Some groups in tropical Africa are relict (suborder Paleoamblypygi). In the Western Palearctic such groups (endemic and relics) are the scorpions of the genera Belisarius and Akrav (with Southamerican affinities). In our time the vast deserts like Sahara and the Arabian desert are a very important barrier for many groups. Key words: Palearctic, Afrotropical, Arachnogeography. Introduction The northern part of Africa is included in the Palearctic Region and the boundary (usualy at 20oN) is separating two Kingdoms – Holarctic and Paleotropical. It is common knowledge that a biogeographical boundary is not a line, but rather a more or less wide transitional zone. We have also to take into account the historical changes during the last several thousand years. Part of these changes is due to climatic factors, other – to human activities (also causing changes in the climate), like deforestation, diverting of rivers, etc. The traditional zoogeographic regions are delimitated mainly on the distribution of terrestrial vertebrates. The difference between the regions and kingdoms are usually on much higher taxonomical level when we consider vertebrates, than with the Arachnida. Differences between Afrotropical and Neotropical regions, or between Holarctic and Paleotropical are between orders or suborders and very much between families. Historically it was not as it is today. In green Sahara and Mediterranean Africa lived elephants, crocodiles, giraffes, in Atlas mountains there were until recently ostriches, lions and bears. They were exterminated by Man. We do not speak about geological periods when these animals (plus Tubulidentata, Marsupialia, tapirs and many others) lived in Europe. The present day biogeographical subdivision should consider the picture of the last several thousand years. We don‘t know what was the distribution of many Arachnids over the green Sahara. It was not influenced by the rare human population during the millenia, as it certainly was in Europe and North America with the disappearing of forests and their replacement with anthropogenic landscape. Important were also new crops like maiz and potatoes, chemization and other kinds of human intruding into the ecosystems. Ecol. Mont., 7, 2016, 464-506 BERON If we follow the classical subdivision (Africa south of Sahara and the southernmost Arabia form the Afrotropical Region), north of this ―line‖ is the Palearctic (different subregions). This ―line‖ (actually transitional zone) is separing two kingdoms, so differences should be substantial. Let us check how the known distribution of Arachnida fits into the classical scheme. Geography and General Zoogeography of Western Palearctic Here Western Palearctic is understood as embracing Europe, Africa North of 20oN and SW Asia (from Bosphorus to Sind). Included is also Siberia west of Yenisey (Johanssen‘s line). Europe is divided into Eurosiberian and Mediterranean Subregions. North Africa near Mediterranean Sea has also Mediterranean fauna, to the South it changes into Saharo-Sindian desert fauna. Neither Europe, nor North Africa and Sahara have always been as they are today. The glaciations changed the older fauna of Europe, than came the destructive human activities. The forests have been very much reduced, and this brought a total desappearence of many invertebrate communities. Such was also the case of the deforestation of circummediterranean territory. South of the barren Atlas mountains once there was a green Sahara, gradually desiccated (Bodenheimer, 1935, Darlington, 1957, de Lattin, 1967, Geptner, 1936, Udvardy, 1975). Analyzing the Zoogeography of the Levant, Por (1975) reached to the conclusion that the Levant province is a peculiar and complex ―subtraction-transition zone‖ (following the expression of Darlington, 1957). The Levant is ―a stretch of land about 150 km wide, wedged in between the [Mediterranean] sea and the Syrio-Arabian desert, stretching from the mouth of the River Orontes and the Amanus and Taurus mountain ranges in the north, to the Isthmus of Suez in the south‖(POR, 1975). This ―subtraction-transition zone‖ between the Palae-arctic and Ethiopian Regions, born by the desertification, is called Palaeo-eremic region. Usually the biota of the Levant is considered to be Palearctic (Mediterranean), but, according to Por (1975), the inclusion of the Old World deserts in the Holarctis is due to a certain ―Europa-centrism‖ of the scientists. ―According to this scheme, the Ethiopis begins only south of the Sahara, in the Savannas, where the last of the typical Palaearctic animals fade out. However, if at all, the connections of of the Palaeo-eremic faunal inventory are much closer to the Ethiopis than to Palaearctis….Our [Israel‘s] typical desert animals, such as scorpions, agamas, gerbils, sand grouse and gazelles, have Ethiopian rather than Holarctic connections, even if some species are so-called ―Mediterraneans‖ (Por, op. cit.). According to the systems of Bodenheimer (1935) and Por (1975), in the Levant could be distinguished four faunal elements: Palaearctic, Palaeo-eremic, Ethiopian and Oriental, with clear prevalence (especially in the north) of the Palaearctics in most of the animal groups. The line along the foothills of Northern Galilee and the Golan Heights was called by Por (1975) ―Nehring Line‖. South of it follows a ―transitional zone‖, where Palaearctic elements mingle with Palaeo-eremic elements. More to the south Por (1975) outlines a ―Bodenheimer Line‖, which is the end of the transitional zone. Follow Ramon Mountains and the mountains of Sinai. The ―Ethiopian element does not prevail in any area. The Oriental species are even more scattered, without showing any geographical pattern. The endemic species among the animals are chiefly of Palaeo-eremic, Ethiopian and also of Oriental origins.…This suggests a higher age of the tropical element, and perhaps a younger and more expansive character of the Holarctic species‖ (Por). In conclusion, ―The Levant province is a meeting place and transitional area between the Palaearctic, Oriental and Ethiopian zoogeographic regions. The broad ―Palaeo-eremic desert belt serves as a filtering barrier between the three faunal regions‖. The islands of Macaronesia (Canaries, Madeira, Azorean Island) are here treated as part of the Palearctic Region, Cabo Verde islands as part of the Afrotropical Region. Africa between 20oN and Zambezi – Kunene (tropical, or intertropical Africa) Geography, General Zoogeography and Paleogeography The sub-Saharan Africa is situated between the usually accepted southern border (actually transition belt) of the Palearctic (Holarctic), a frontier between one kingdom and another (Paleotropica). South of the Sahara follow the belts of semidesert (Sahel) and the different types of savanna. In the described area there are also high mountains with afroalpine vegetation and mountain rainforest. Tropic rain forests are tropical moist forests of semi-deciduous varieties distributed across nine West African countries. In the first half of the 1980s, an annual forest loss of 7200 square kilometers was note down along the Gulf of Guinea, a figure equivalent to 4-5 percent of the total remaining rain forest area. By Ecol. Mont., 7, 2016, 464-506 465 ARACHNOGEOGRAPHICAL COMPARISON BETWEEN WEST PALEARCTIC AND AFROTROPICAL REGION 1985, 72 percent of West Africa's rainforests had been transformed into fallow lands and an additional 9 percent had been opened up by timber exploitation. It is generally believed that firewood provides 75 per cent of the energy used in sub-Sahara Africa. With the high demand, the consumption of wood for fuel exceeds the renewal of forest cover. The rain forests which remain in West Africa now merely are how they were hardly 30 years ago. In Guinea, Liberia and the Ivory Coast, there is almost no primary forest cover left unscathed; in Ghana the situation is much worse, and nearly all the rain forest are cut down. Guinea-Bissau loses 200 to 350 km² of forest yearly, Senegal 500 km² of wooded savanna, and Nigeria 6,000,050,000 of both. Liberia exploits 800 km² of forests each year. Tropical Africa is about 18% of the world total covering 20 million km² of land in West and Central Africa. Recent estimates show that the annual pace of deforestation in the region can vary from 150 km² in Gabon to 2900 km² in Ivory Coast. Remaining tropical forest still cover major areas in Central Africa but are abridged by patches in West Africa. The tropical environment is rich in terms of bio-diversity. Tropical African forest is 18 per cent of the world total and covers over 3.6 million square kilometers of land in West, East and Central Africa. This total area can be subdivided to 2.69 million square kilometers (74%) in Central Africa, 680,000 square kilometers (19%) in West Africa, and 250,000 square kilometers (7%) in East Africa. In West Africa, a chain of rain forests up to 350 km long extends from the eastern border of Sierra Leone all the way to Ghana. In Ghana the forest zone gradually dispels near the Volta river, following a 300 km stretch of Dahomey savanna gap. The rain forest of West Africa continues from east of Benin through southern Nigeria and officially ends at the border of Cameroon along the Sanaga river.