* 4 ways a newcomer may impact local biodiversity:
* Easiest to detect and quantify
* Greatest threat to natives
* E.g. decline of water vole (Arvicola terrestris) attributed to accidental introduction of American mink (escaped from fur industry); impact also exacerbated by agricultural conversion (loss of good quality riparian habitats)
* Water vole reintroduction projects assessed relative impacts of mink predation and habitat quality on survival of released water voles mink control most important determinant of success; where control successful, habitat quality determined survival rates ...view middle of the document...
often as consequences of humans transporting organisms beyond natural range)
* UK: 23% and 12% of BAPs for habitats and species cite non-natives as problematic
* Introduced species may weaken an ecosystem/tip native biodiversity over a cliff edge to which it has already been brought by population fragmentation, habitat degradation/loss, etc.
* Scottish wildcat dilemma:
* Hybridization between wildcats and domestic cats
* Wildcats isolated in Britain after the end of the last ice age (~10,000 ya); joined by domestic cats 2000+ y.a.; have been interbreeding ever since.
* Scottish wildcats = protected by law, whereas feral domestic cats are regarded as a pest
* Debate as to whether they are different species
* Law gives no protection to hybrids, but significant proportion of remaining wildcat genes may be packaged in hybrid bodies; no specimens of pre-Iron Age Scottish wildcats from which to judge original natural variation
* 1. How to define Scottish wildcats?
* 2. How to conserve + restore their populations?
* May be defined on pelage characters, but these individuals may be scattered among an ocean of hybrids and feral domestics
* Saving wildcat genes may necessitate conserving some cats in which wild cat and domestic cat genes are packaged together
* Golden and capped langurs in Bhutan:
* Building of 5 suspension bridges has facilitated their intermixing/breeding
* Cross-breds could be shot to protect the endemism of the golden langur, but should they be?
* Every species has at least one macroparasite and one microparasite
* Some parasites are host-specific; others are more generalist; have different impacts on different host species
* Parasites may contribute enormously to community biomass + biodiversity and may be important component of communities/ecosystems
* By definition, parasites have a negative impact on their host, depleting energy/nutrient reserves to significantly reduce fecundity or cause death.
* Effect may be negligible to host or cause diseases with devastating impacts on the population
* E.g. affect species viability
* On the other hand, credible theory that parasites have driven evolution of many species
* Parasites may regulate host population by affecting fecundity and mortality rates, may change an individual’s behavior (e.g. eye fluke that passes between aquatic snails, fish and birds)
* Diseases tend to gain our attention when they threaten human interests
* R0 (contact rate)= average number of new individuals that become infected from one individual. Not constant and will change over time as the number of susceptibles decreases as infection spreads; also varies between individuals. Provides a good measure of parasite ‘fitness’ in a host population.
* R0 must equal 1 or greater in order to spread through a population.
* Method of transmission...