Alexandre Miró

Local and regional founder effects in lake zooplankton persist after thousands of years despite high dispersal potential

We reconstructed the genetic structure of a planktonic crustacean Daphnia longispina living in high mountain lakes and ponds in the Pyrenees to investigate whether it was shaped by persistent founder effects originating shortly after the last glacial maximum or by ongoing dispersal and effective migration (gene flow). We found that the genetic structure can largely be explained by a single colonization event following gradual deglaciation of the Pyrenees ~10 000–15 000 years ago. Nuclear genetic diversity declined steeply from southeast to northwest, suggestive of serial colonization of available habitats with advancing deglaciation. The spatial genetic structure suggests that founder effects were major determinants of the present‐day diversity, both at the catchment level and at the level of individual water bodies, further supporting extremely low effective migration rates. This study reveals a prime example of a founder effect that is both long lasting and maintained at small spatial scales. Our data suggest a process of isolation by colonization as a result of strong priority effects and monopolization. We found evidence for the spread of haplotypes with Pyrenean ancestry across the Palaearctic over distances up to 5500 km, although the local genetic structure after colonization was hardly influenced by contemporary dispersal. Finally, our data also suggest that mitochondrial mutation rates in the studied populations were seven times higher than typically assumed. Overall, we show that founder effects can persist for centuries even at small spatial scales at which the potential for dispersal is high.

Habitat requirements and conservation needs of peripheral populations : the case of the great crested newt (Triturus cristatus) in the Scottish Highlands

Edge populations are of conservation importance because of their roles as reservoirs of evolutionary potential and in understanding a given species’ ecological needs. Mainly due to loss of aquatic breeding sites, the great crested newt Triturus cristatus is amongst the fastest declining amphibian species in Europe. Focusing on the north-westerly limit of the T. cristatus range, in the Scottish Highlands, we aimed to characterise habitat requirements and conservation needs of an isolated set of edge populations. We recorded 129 breeding pond-related environmental parameters, and used a variable selection procedure followed by random forest analysis to build a predictive model for the species’ present occurrence, as well as for population persistence incorporating data on population losses. The most important variables predicting T. cristatus occurrence and persistence were associated with pond quality, pond shore and surrounding terrestrial habitat (especially mixed Pinus sylvestris–Betula woodland), and differed from those identified in the species’ core range. We propose that habitat management and pond creation should focus on the locally most favourable habitat characteristics to improve the conservation status and resilience of populations. This collaborative work, between conservation agencies and scientific researchers, is presented as an illustrative example of linking research, management and conservation.

Why Should We Preserve Fishless High Mountain Lakes

High mountain lakes are originally fishless, although many have had introductions of non-native fish species, predominantly trout, and recently also minnows introduced by fishermen that use them as live bait. The extent of these introductions is general and substantial often involving many lakes over mountain ranges. Predation on native fauna by introduced fish involves profound ecological changes since fish occupy a higher trophic level that was previously inexistent. Fish predation produces a drastic reduction or elimination of autochthonous animal groups, such as amphibians and large macroinvertebrates in the littoral, and crustaceans in the plankton. These strong effects raise concerns for the conservation of high mountain lakes. In terms of individual species, those adapted to live in larger lakes have suffered a higher decrease in the size of their metapopulation. This ecological problem is discussed from a European perspective providing examples from two study areas: the Pyrenees and the Western Italian Alps. Species-specific studies are urgently needed to evaluate the conservation status of the more impacted species, together with conservation measures at continental and regional scales, through regulation, and at local scale, through restoration actions, aimed to stop further invasive species expansions and to restore the present situation. At different high mountain areas of the world, there have been restoration projects aiming to return lakes to their native fish-free status. In these areas autochthonous species that disappeared with the introduction of fish are progressively recovering their initial distribution when nearby fish-free lakes and ponds are available.

Testing the validity of a commonly-used habitat suitability index at the edge of a species’ range: great crested newt Triturus cristatus in Scotland

Habitat Suitability Indices (HSI) are widely used in conservation and in pre-development surveying. We tested a commonly-used HSI to assess its effectiveness at predicting the presence of a European protected species, the great crested newt Triturus cristatus , at the edge of its range. This HSI is used to understand species’ conservation needs, and in assessing the need for, and designing, mitigation. Given the cost of surveying to developers, it is essential that they can have confidence in the index used in targeting work and in Environmental Impact Assessments. We found that nine of the ten factors which make up the HSI are robust in the region, even in a disjunct population believed to have been isolated for around 3000 years. However, we propose modification of the geographic factor, based upon an improved knowledge of the species’ distribution since the HSI was originally devised.