02748nas a2200217   4500008004100000022001400041245010500055210006900160300001400229520208000243653002302323653002002346653002002366653001502386653001702401100001602418700001602434700001902450700002102469856004002490       2016                        eng d  a2045-775800aChromosome numbers in three species groups of freshwater flatworms increase with increasing latitude0 aChromosome numbers in three species groups of freshwater flatwor  an/a–n/a3 aPolyploidy in combination with parthenogenesis offers advantages for plasticity and the evolution of a broad ecological tolerance of species. Therefore, a positive correlation between the level of ploidy and increasing latitude as a surrogate for environmental harshness has been suggested. Such a positive correlation is well documented for plants, but examples for animals are still rare. Species of flatworms (Platyhelminthes) are widely distributed, show a remarkably wide range of chromosome numbers, and offer therefore good model systems to study the geographical distribution of chromosome numbers. We analyzed published data on counts of chromosome numbers and geographical information of three flatworm “species” (Phagocata vitta, Polycelis felina and Crenobia alpina) sampled across Europe (220 populations). We used the mean chromosome number across individuals of a population as a proxy for the level of ploidy within populations, and we tested for relationships of this variable with latitude, mode of reproduction (sexual, asexual or both) and environmental variables (annual mean temperature, mean diurnal temperature range, mean precipitation and net primary production). The mean chromosome numbers of all three species increased with latitude and decreased with mean annual temperature. For two species, chromosome number also decreased with mean precipitation and net primary production. Furthermore, high chromosome numbers within species were accompanied with a loss of sexual reproduction. The variation of chromosome numbers within individuals of two of the three species increased with latitude. Our results support the hypothesis that polyploid lineages are able to cope with harsh climatic conditions at high latitudes. Furthermore, we propose that asexual reproduction in populations with high levels of polyploidization stabilizes hybridization events. Chromosomal irregularities within individuals tend to become more frequent at the extreme environments of high latitudes, presumably because of mitotic errors and downsizing of the genome.10aGeographical range10aparthenogenesis10aPlatyhelminthes10apolyploidy10areproduction1 aLorch, Sven1 aZeuss, Dirk1 aBrandl, Roland1 aBrändle, Martin  uhttp://dx.doi.org/10.1002/ece3.196900376nas a2200085   4500008004100000245008400041210006900125100001600194856008000210       1978                        eng d00aThe planarians (Turbellaria: Tricladida, Paludicola) of Lake Ohrid in Macedonia0 aplanarians Turbellaria Tricladida Paludicola of Lake Ohrid in Ma1 aKenk, Roman  uhttp://www.sil.si.edu/smithsoniancontributions/Zoology/pdf_hi/SCTZ-0280.pdf00677nas a2200169   4500008004100000022001400041245020100055210006900256260001200325300001100337490000700348100003200355700001800387700001900405700002000424856006300444       2013                        eng d  a1090-692400aSubterranean Aquatic Planarians of Sardinia, with a Discussion on the Penial Flagellum and the Bursal Canal Sphincter in the Genus <i>Dendrocoelum</i> (Platyhelminthes, Tricladida, Dendrocoelidae)0 aSubterranean Aquatic Planarians of Sardinia with a Discussion on  c08/2013  a93-1120 v751 aStocchino, Giacinta, Angela1 aSluys, Ronald1 aMarcia, Palolo1 aManconi, Renata  uhttp://www.caves.org/pub/journal/PDF/v75/cave-75-02-93.pdf