1887

n Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie - Verspreiding en habitats van Kuiper, 1956 (Bivalvia : Sphaeriidae) soos weerspieël deur die rekords van die Nasionale Varswaterslakversameling van Suid-Afrika : research and review article

Volume 27, Issue 3
  • ISSN : 0254-3486
  • E-ISSN: 2222-4173

Abstract


The genus Pisidium includes some of the smallest bivalves in the family Sphaeriidae. The distribution of this group is cosmopolitan and they can utilize virtually any freshwater habitat, including peat bogs. Without doubt their centre of evolution lies in the Holarctic Region and the origin of Pisidium is considered to be Mesozoic. This article focuses on the geographical distribution and habitats of , the most well represented species of this genus in the database of the National Freshwater Snail Collection (NFSC) of South Africa.
Details pertaining to the habitats of the 639 samples of as recorded at the time of collection were extracted from the database of the NFSC. The number of loci (1/16 th square degrees) in which the 639 collection sites were located, was distributed in pre-selected intervals of mean annual air temperature and rainfall, as well as intervals of mean altitude, to illustrate the frequency of occurrence within specific intervals. A temperature index was calculated for all mollusc species in the database from their frequencies of occurrence within the selected intervals and the results used to rank them in order of their association with low to high climatic temperatures. To evaluate the significance of the difference between frequencies of occurrence in, on, or at the various options for each parameter investigated, chi-square values were calculated. Furthermore, an effect size value was calculated to determine the contribution of each parameter towards establishing the geographical distribution of this species as reflected by the data in the database. Additionally, a multivariate analysis in the form of a decision tree was constructed from the data which enabled the selection and ranking of those variables that maximally discriminated between the frequency of occurrence of in, on, or at the various options for each parameter as compared to all other mollusc species in the database.

Hierdie artikel fokus op die geografiese verspreiding en habitats van , een van die kleinste varswatermossels teenwoordig in Suid-Afrika, soos weerspieël deur die 639 monsters wat in die databasis van die Nasionale Varswaterslakversameling van Suid-Afrika (NVWSV) opgeneem is. Hierdie spesie is hoegenaamd nie in Limpopo aangetref nie en is yl versprei in Oos-, Noord- en Wes-Kaap. Hierteenoor is dit die mees wydverspreide verteenwoordiger van die Mollusca in Lesotho. Besonderhede van elke habitat sowel as hoogte bo seevlak, lugtemperatuur en reënval van elke lokaliteit is statisties verwerk en word deurtastend bespreek. is in 13 van die 14 tipes waterliggame wat in die databasis verteenwoordig word, gevind maar verreweg die grootste getal monsters was van moerasse afkomstig en die meerderheid monsters is gerapporteer uit habitats waarvan die watertoestande as standhoudend, helder, vars en staande aangeteken is. Die resultate van 'n geïntegreerde besluitnemingsboom- en effekgrootte-analise het getoon dat temperatuur, hoogte bo seevlak, waterliggame en substratum die gedokumenteerde geografiese verspreiding van hierdie spesie, soos weerspieël deur die data in die databasis, betekenisvol beïnvloed het. In die lig van die groot verskeidenheid van geleenthede wat in die literatuur gerapporteer is waarvolgens -spesies passief kan sprei, is die outeurs van mening dat die skynbare afwesigheid van in groot dele van Suid-Afrika waarskynlik aan ongunstige omgewingstoestande eerder as 'n gebrek aan geleenthede om te sprei, toegeskryf kan word. Die haalbaarheid om vir die monitering van swaarmetale te benut, behoort ondersoek te word, asook sy potensiaal om as tussengasheer vir parasitiese helminte op te tree.

Loading full text...

Full text loading...

Loading

Article metrics loading...

/content/aknat/27/3/EJC20431
2008-09-01
2019-08-17

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error