Diversity Of Terrestrial Isopods Research Articles

Étude de la diversité des Isopodes Terrestres dans les Agrosystèmes Oasiens de la Tunisie

Dans cette étude, plusieurs compagnes d’échantillonnage d’isopodes terrestres ont été réalisées dans différentes oasis du Sud Tunisien ainsi que dans d’autres sites hors oasis. Les résultats ont permis de recenser : dans les oasis, une douzaine d’espèces appartenant à trois familles Porcellionidae, Armadillidiidae et Armadillidae et dans les autres sites hors oasis, seulement 5 espèces faisant partie des 2 familles Porcellionidae et Agnaridae. Cette différence de la richesse spécifique pourrait être expliquée par les conditions climatiques différentes entre les deux sites étudiés. En effet, la majorité des espèces collectées dans les oasis sont caractéristiques des zones humides témoignant du rôle important des oasis dans le maintien de cette diversité spécifique des isopodes terrestres.

Faunistic data and biogeography of terrestrial isopods from Tunisian wetlands

AbstractIn Tunisia, while wetlands are considered as remarkable habitats for their faunal and floral diversity, few studies on the biogeography and the diversity of terrestrial isopods were performed. To fill this gap, we carried out a field study in the supralittoral zone of 146 Tunisian wetlands belonging to eight types (lagoon, river, lake, sebkha, dam, hill reservoir, beach and chott) and to five bioclimatic zones (humid, subhumid, semi‐arid, arid and Saharan). Field work was carried out in spring 2010. Terrestrial isopods were collected in the morning by hand search each time with the same sampling effort. During the study, 22 species of terrestrial isopods belonging to nine families were collected. Porcellio variabilis, Porcellio laevis, Chaetophiloscia elongata and Armadillidium pelagicum are the most common species identified. From the northern to the southern regions, a gradual decrease in species richness has been shown. The identified species belonged to different biogeographical categories: Mediterranean, Mediterranean‐Atlantic, North Africa with circum‐Sicilian islands, semi‐arid and Saharan species. Some of these species are endemic to Tunisia (Porcellio dominici) or to North Africa (Armadillidium sulcatum, Armadillidium tunisiense, Porcellio marginenotatus and P. variabilis). Terrestrial isopod species differ according to wetland type and bioclimatic zone.

Diversity of terrestrial isopods in the northern Tunisian wetlands

AbstractTo evaluate the influence of wetland types on the distribution of terrestrial isopods, species richness, relative abundance and diversity indices were studied in the supralittoral zone of 95 wetlands in the north‐western of Tunisian dorsal, belonging to six types: lagoon, hill reservoir, river, dam, lake and sebkha. We tested the following hypothesis: (i) is isopod diversity influenced by wetland types? (ii) is isopod diversity influenced by bioclimatic zones? and (iii) what are the environmental factors influencing isopod distribution? A total of 3255 individuals belonging to twenty species of terrestrial isopods were captured. Species richness differs significantly between wetland types. A highly significant positive relationship between species richness and both humidity and altitudinal gradient was described. The dendrogram of similarities showed a divergence of the lagoons compared to the remaining wetland types.

The diversity of terrestrial isopods in the natural reserve “Saline di Trapani e Paceco” (Crustacea, Isopoda, Oniscidea) in northwestern Sicily

Ecosystems comprising coastal lakes and ponds are important areas for preserving biodiversity. The natural reserve “Saline di Trapani e Paceco” is an interesting natural area in Sicily, formed by the remaining strips of land among salt pans near the coastline. From January 2008 to January 2010, pitfall trapping was conducted in five sampling sites inside the study area. The community of terrestrial isopods was assessed using the main diversity indices. Twenty-four species were collected, only one of them endemic to western Sicily: Porcellio siculoccidentalis Viglianisi, Lombardo & Caruso, 1992. Two species are new to Sicily: Armadilloniscus candidus Budde-Lund, 1885 and Armadilloniscus ellipticus (Harger, 1878). This is high species richness for a single reserve in Sicily. The extended sampling period also allowed us to study species phenology. Most of the species exhibited higher activity in spring than in autumn while some species also exhibited lower activity in the summer. The species richness revealed that the study area is in an acceptable conservation status; Shannon and Pielou indices also confirmed a more or less even distribution of individuals belonging to different species.

Diversity of terrestrial isopods in a protected area characterized by salty coastal ponds (Vendicari, Sicily)

The diversity of Oniscidean isopods was studied in Vendicari, a protected area in southeastern Sicily characterized by salty ponds separated from the sea by narrow bands of land. Samples were collected in pitfall traps placed in transects from the coastline to the ponds and from the ponds inland. Twenty-three species were identified, only seven of which were present at all sampling sites. Shannon's diversity and Pielou's evenness indices revealed higher values in the spring and autumn; activity indices were also calculated for each species for all months of the year. Similarity among sampling sites was evaluated qualitatively with Jaccard's index and quantitatively with Sørensen's index. The ponds seem to play the same role as the seacoasts regarding species zonation.

Oniscidea diversity across three environments in an altitudinal gradient in northeastern Rio Grande do Sul, Brazil

The diversity of Oniscidea across a 1000-m altitudinal gradient comprising three distinct environments—the coastal plain, the highland slopes, and the highlands—was described and analysed. We employed 1 h-long exploratory manual sampling at 41 sites. Fourteen species were identified, of 818 individuals collected. Sampling-effort curves stabilised for all three environments; analytical estimates of species richness did not exceed the observed value. Abundance did not vary significantly among environments, and local species richness differed only marginally. However, the Shannon diversity index for local sites indicated highland slopes to be significantly more diverse than the coastal region; the same was true for bootstrap estimates at the regional level. Two species appeared in all three environments, comprising 72.7% of the abundance. The coastal region and highlands had one exclusive species each, and the highland slopes had three. The first two environments are more similar to each other than to the slopes, although they are not contiguous. The altitudinal gradient of diversity was hump-shaped, because the highland slopes were most diverse. The reasons for this pattern are not biogeographical; that is, the highland slopes are not a contact zone between the highlands and the coast. A complete explanation depends upon better understanding of the effect of soil type and terrain slope on the diversity of terrestrial isopods.

Armadillidae (Crustacea: Isopoda) from Lord Howe Island: new taxa and biogeography

Lord Howe Island and associated island, Ball’s Pyramid, in the Tasman Sea between Australia and New Zealand, have a surprising diversity of terrestrial isopods. New species in the genera Pyrgoniscus, Cubaris and a new genus (Stigmops, n.gen.) of the family Armadillidae are described from Australian Museum collections made on Lord Howe Island. Two species, formerly placed in Anchicubaris, are moved to the new genus. Anchicubaris is revised to show how it differs from the new genus. With these changes, species of Anchicubaris no longer occur on Lord Howe Island. A lectotype for Anchicubaris fongosiensis is assigned. The homonymy of Cubaris granulatus Lewis, 1998b is resolved with a new name and a type species for the genus Sphenodillo Lewis, 1998b is assigned. A key to Lord Howe Armadillidae is provided. The biogeography of Armadillidae genera on Lord Howe Island shows possible links to neighbouring regions of New Caledonia and eastern Australia. Because relationships of species in the large genera Cubaris and Pyrgoniscus are unknown, precise area relationships cannot be estimated. The high diversity and presence of armadillids on the nearby rock, Balls Pyramid, suggests that the Lord Howe fauna is a contracted remnant of a much larger Pleistocene fauna, when lowered sea levels provided interconnections and much larger areas. LILLEMETS, BIRGITTA, AND GEORGE D.F. WILSON, 2002. Armadillidae (Crustacea: Isopoda) from Lord Howe Island: new taxa and biogeography. Records of the Australian Museum 54(1): 71–98. Records of the Australian Museum (2002) Vol. 54: 71–98. ISSN 0067-1975 www.amonline.net.au/pdf/publications/1360_complete.pdf Lord Howe Island is a small, subtropical island situated on the Lord Howe Rise in the Tasman Sea approximately 700 km northeast of Sydney (31°33'S 159°05'E, Fig. 1). The island covers an area of approximately 15 km2 and is the eroded remnant of volcanic activity 6–7 million years ago. The main island is dominated by two peaks, Mount Gower (875 m) and Mount Lidgebird (777 m) in the south, hills in the north (up to 200 m high) and lowlands in the middle of the island (Hutton, 1986). The Lord Howe Rise, upon which the island sits, was separated first from New Zealand and later from Australia approximately 80 million years ago (Hutton, 1986). The Rise has been subject to several sea level changes during which exposed islands have acted as permanent refuges for indigenous organisms or as “stepping stones” for organisms from other landmasses (Clark & Pickard, 1977). The flora and fauna have close relatives in Australia, New Zealand, New Caledonia and Norfolk Island, but its long-term isolation has resulted in a high proportion of endemic species. These species were largely undisturbed until the first recorded human contact in 1788 when Europeans landed on the island. A permanent settlement was founded in 1834 (Hutton, 1986).