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Evolutionary patterns of Pseudamnicola D. Delicado et al.

barriers that maintain isolated the split populations (Gavri- genus, Corrosella, designating Corrosella falkneri as its type
lets & Losos 2009; Glaubrecht 2011). However, a barrier species. However, given the lack of other diagnostic char-
does not need to be a geographic entity and may be also acters for identifying each genus, Boeters (1984) concluded
considered as a sudden shift of environmental conditions that Corrosella should be a subgenus within Pseudamnicola.
where the suitable habitat for a species ends (Fitzpatrick This exemplification demonstrates the necessity of further
et al. 2009; Pyron & Burbrink 2010). For instance, changes studies to produce more exhaustive morphological and ana-
in the chemical parameters of the aquatic environment can tomical descriptions as well as well-supported, consistent
favour allopatric separation between populations, especially phylogenies. Hydrobiids s. str., and especially Pseudamnicola,
for those groups that exhibit scarce dispersal abilities and have weakly sculptured shells that exhibit scarce number of
opportunities, resulting in restrictive distributions (Ponder diagnostic characters (Arconada & Ramos 2003; Bichain
& Colgan 2002; Perez et al. 2005). Freshwater gastropods, et al. 2007; Strong et al. 2008) and therefore making it dif-
which are typically habitat specialist, gather those proper- ficult to establish clear species boundaries. By incorporating
ties of limited dispersal capabilities and narrow-ranged dis- molecular techniques and morphological and anatomical
tributions and tend therefore to be strongly affected by descriptions, Delicado et al. (2012, 2013) and Delicado &
variation in their habitat. For this reason, they represent an Ramos (2012) identified seven new species of P. (Corrosel-
ideal model to investigate speciation processes associated la), thus increasing the known species richness of this sub-
with isolating mechanisms (e.g. Mav arez et al. 2002; Albr- genus from five to 12. These studies not only revealed
echt et al. 2007; von Rintelen et al. 2012; Schreiber et al. cryptic species diversity within the genus, but also differ-
2012; Delicado et al. 2013). In particular, one potential ences in habitat requirements and distribution range
candidate taxon that may provide valuable information between the two subgenera. In fact, Delicado et al. (2013)
about evolutionary processes in different environments is found that these 12 species of P. (Corrosella) are mainly
the microgastropod family Hydrobiidae Stimpson, 1965. restricted to headwaters of mountainous regions of the Ibe-
Hydrobiids are known to be presumably the most spe- rian Peninsula and south of France, whereas around 45
cies-rich family of freshwater gastropods, characterized nominal species of P. (Pseudamnicola) have been recorded in
besides by a long evolutionary history, wide distribution streams, lakes and low river courses of several Mediterra-
and ecological and morphological diversity. Recently, Wil- nean islands and mainland territories (Pallary 1926; Sch€utt
ke et al. (2013) published the most complete phylogenetic & Bilgin 1970; Boeters 1976; Sch€utt & Sesen 1993; Ghamizi
hypothesis on the superfamily Rissooidea (newly considered et al. 1997; Gl€ oer et al. 2010; Bank 2011). These current
as Truncatelloidea: Criscione & Ponder 2013) delineating biodiversity patterns suggest different dispersal strategies
the family Hydrobiidae s. str., as well as its distribution between the subgenera: P. (Corrosella) may scarcely disperse
range mainly to the Western Palearctic and eastern Nearc- via habitat connection and suitability of habitats, which
tic. Accordingly, this family comprises around 70 genus- results in a pattern of isolation by distance (Wright 1943),
level and 550 species-level taxa. Moreover, the diversity of whereas the wider distribution range of P. (Pseudamnicola)
habitat types which they inhabit is also remarkable. may be a result of long-distance dispersions possibly via
Approximately 35 hydrobiid species are brackish, and the passive mechanisms (Delicado et al. 2013, 2014).
rest occurs in freshwater ecosystems such as springs (the Previous works revealed that diversification patterns of
majority of the species according to Strong et al. 2008), Pseudamnicola species belonging to the same subgenus are
ponds, lakes and rivers. One inference of the hydrobiid related to geographic isolation rather than ecological diver-
phylogeny published by Wilke et al. (2013) is that species gence (Delicado et al. 2013, 2014). Beyond what has been
from the same subfamily seem to share similar ecological shown by these studies, we hypothesize that the temporal
requirements. A notable exception seems to be the genus history and mode of diversification of the exclusively
Pseudamnicola Paulucci 1878, whose evolutionary history springsnail P. (Corrosella) species should differ of P. (Pseu-
appears to have been influenced by a transition between damnicola) species, which are more euryhaline in habit.
two different environments. Consequently, this group may Springs and headwaters of streams, the habitat type of
be considered one of the key elements to understand the P. (Corrosella) species, typically present more stable condi-
origin and causes of the great hydrobiid diversity. tions, being, however, more vulnerable to severe environ-
Pseudamnicola was first proposed by Paulucci (1878) to mental changes (as flooding or desiccation, pollution, etc.),
differentiate between European and American Amnicola which makes them isolated habitats and limiting factor for
Gould & Haldeman, 1840 species, characterizing both dispersion (Wilke et al. 2010). Moreover, due to their spa-
groups mainly by their conchological features. Nearly a tial location in small areas at high altitudes, most of these
century later, Boeters (1970) studied the genus anatomically springsnail species occur in a very confined number of
and based on differences in female genitalia, defined a new localities or even are single-site endemisms, increasing their

404 ª 2015 Royal Swedish Academy of Sciences, 44, 4, July 2015, pp 403–417