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The ability of aquatic insects to colonize Earth’s most remote freshwater habitats, such as those of islands and deserts, is limited to select taxa. Among black flies, the premiere colonization specialist is Simulium ruficorne Macquart, the only species known from both the Afrotropical and Palearctic regions. We investigated the cytogenetics of S. ruficorne to gain insight into its wide geographic distribution and ability to colonize oceanic islands and deserts. On the basis of larval polytene chromosomes from 14 locations, we documented 17 novel and previously known chromosomal rearrangements and established five cytoforms (A1, A2, B, C, and D), of which probably four (A1/A2, B, C, and D) are distinct species and two (A1 and A2) represent sex-chromosome polymorphism involving a heteroband in the long arm of chromosome III. The chromosome restructuring phenomena associated with the five cytoforms are consistent with the trend in the Simuliidae that one and the same rearrangement can assume different functions in the various descendants of a common ancestor in which the rearrangement was polymorphic. The most widely distributed cytoforms are A1 and A2, which are found in North Africa, the Canary Islands, and Majorca. Simulium ruficorne, the only known black fly in the Hoggar Mountains of the central Sahara Desert, represents a cohesive population of cytoform A1 little differentiated from other North African populations of A1 and A2. Cytoform B inhabits the West African mainland, cytoform C is on Tenerife, and cytoform D is on Cape Verde. We suggest that dispersal and colonization specialists, such as S. ruficorne, are multivoltine inhabitants of temporary streams, and must relocate as their habitats deteriorate. Simulium ruficorne, therefore, should have adaptations that contribute to successful dispersal and colonization, perhaps largely physiological in nature, such as tolerance of high temperatures and droughts. [ABSTRACT FROM AUTHOR]

Modern conservationists call for long term genetic monitoring datasets to evaluate and understand the impact of human activities on natural ecosystems and species on a global but also local scale. However, long-term monitoring datasets are still rare but in high demand to correctly identify, evaluate and respond to environmental changes. In the presented study, a population of the riverine dragonfly, Orthetrum coerulescens (Odonata: Libellulidae), was monitored over a time period from 1989 to 2013. Study site was an artificial irrigation ditch in one of the last European stone steppes and “nature heritage”, the Crau in Southern France. This artificial riverine habitat has an unusual high diversity of odonate species, prominent indicators for evaluating freshwater habitats. A clearing of the canal and destruction of the bank vegetation in 1996 was assumed to have great negative impact on the odonate larval and adult populations. Two mitochondrial markers (CO1 & ND1) and a panel of nuclear microsatellite loci were used to assess the genetic diversity. Over time they revealed a dramatic decline in diversity parameters between the years 2004 and 2007, however not between 1996 and 1997. From 2007 onwards the population shows a stabilizing trend but has not reached the amount of genetic variation found at the beginning of this survey. This decline cannot be referred to the clearing of the canal or any other direct anthropogenic impact. Instead, it is most likely that the populations’ decay was due to by extreme weather conditions during the specific years. A severe drought was recorded for the summer months of these years, leading to reduced water levels in the canal causing also other water parameters to change, and therefore impacting temperature sensitive riverine habitat specialists like the O. coerulescens in a significant way. The data provide important insights into population genetic dynamics and metrics not always congruent with traditional monitoring data (e.g. abundance); a fact that should be regarded with caution when management plans for developed landscapes are designed. [ABSTRACT FROM AUTHOR]

Background: Marine species have colonized extreme environments during evolution such as freshwater habitats. The amphidromous teleost fish, Galaxias maculatus is found mainly migrating between estuaries and rivers, but some landlocked populations have been described in lakes formed during the last deglaciation process in the Andes. In the present study we use mtDNA sequences to reconstruct the historical scenario of colonization of such a lake and evaluated the osmoregulatory shift associated to changes in habitat and life cycle between amphidromous and landlocked populations. Results: Standard diversity indices including the average number of nucleotide differences (Π) and the haplotype diversity index (H) indicated that both populations were, as expected, genetically distinctive, being the landlocked population less diverse than the diadromous one. Similarly, pairwise GST and NST comparison detected statistically significant differences between both populations, while genealogy of haplotypes evidenced a recent founder effect from the diadromous stock, followed by an expansion process in the lake. To test for physiological differences, individuals of both populations were challenged with a range of salinities from 0 to 30 ppt for 8 days following a period of progressive acclimation. The results showed that the landlocked population had a surprisingly wider tolerance to salinity, as landlocked fish survival was 100% from 0 to 20 ppt, whereas diadromous fish survival was 100% only from 10 to 15 ppt. The activity of ATPase enzymes, including Na+/K+-ATPase (NKA), and H+-ATPase (HA) was measured in gills and intestine. Activity differences were detected between the populations at the lowest salinities, including differences in ATPases other than NKA and HA. Population differences in mortality are not reflected in enzyme activity differences, suggesting divergence in other processes. Conclusions: These results clearly demonstrate the striking adaptive changes of G. maculatus osmoregulatory system, especially at hyposmotic environments, associated to a drastic shift in habitat and life cycle at a scale of a few thousand years. [ABSTRACT FROM AUTHOR]