Ecological niche relations of indigenous and invasive crayfish (Astacoidea) in SloveniaMartina Jaklič
, 2016, doktorska disertacija
Opis: In this study, realised and fundamental niches were combined between studied ICS (Austropotamobius torrentium (Schrank, 1803), Austropotamobius pallipes (Lereboullet, 1858), Astacus astacus (Linnaeus, 1758)) and NICS (Pacifastacus leniusculus (Dana, 1852), Orconectes limosus (Rafinesque, 1817), Cherax quadricarinatus (von Martens, 1868)). The realised niche was described by population characteristics. P. leniusculus showed similar annual cycle than ICS, but on the other hand it showed higher population density, shorter breeding period, and better individual condition (estimated with SMI) comparing to the ICS. These are its advantages over ICS, which increase its potential for the invasiveness. The most pronounced this threat is to A. astacus, with which it has the most similar/ overlapping realised niche. Similar was observed comparing the ICS and NICS fundamental niches presented by selected physiological measurements (maximal food (Cmax) and oxygen consumption (Rn), concentration of haemocyanin in haemolymph (Hc), electron transport system (ETS) activity and potential growth scope (PGS). As a result of higher plasticity and adaptation to varied environmental conditions, NICS expressed different physiological response to temperature at cellular (ETS activity) and organism (Cmax, Rn, PGS) level. Similar fundamental characteristics (expressed with thermal optimums) were found between P. leniusculus and ICS, while optima for O. limosus and C. quadricarinatus were more narrow and higher (above 22 °C and 30 °C). Modelling of thermal niches showed differences mostly among species on cellular level (in ETS activity). This was a new approach and support for better estimation of success and proliferation of new invaders. Furthermore, C. Quadricarinatus, found for the first time as established population in temperate climate of Europe (in Slovenia in 2009), was used in this study, as a model organism, to show that the combination of fundamental and realised thermal niche, as well as ecophysiological and field research can constitute an important input to the model for estimating the risk associated with C. quadricarinatus. It is rarely possible to observe the development of new invaders in the new environment, therefore monitoring of the C. quadricarinatus through the three growth period (1-lag phase, 2-log phase, 3-stable phase), was unique example in the invasive biology. After extremely increasing the population in 2011 and 2012 (for 7.7 - 10.1 % per month) the population developed and stabilised in March 2012. Based on these high numbers of field and lab data, the TIRI (Thermal Invasive Risk Index) was developed to produce instant results that may be satisfactory for evaluation of different degrees of invasiveness. We found that the oxbow lake Topla had no lethal days (no. of days when water temperature is below or above temperature of death) in comparison with the adjacent rivers where the number of lethal days probably constitutes an important barrier for species spreading. Therefore, we concluded that C. quadricarinatus could potentially reproduce in the adjacent rivers, but survival of the brood is doubtful, especially due to previous results concerning critical min/max temperatures.
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Ključne besede: potočni raki, jelševec, koščak, koščenec, signali rak, trnavec, rdečeškarjevec, sezonska dinamika, termalna toleranca, temeljna ekološka niša, realizirana niša, potencialna invazivnost
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