Crunoecia irrorata (Curtis) (Trichoptera: Lepidostomatidae) and conservation of boreal springs: indications of clustering of red‐listed species

Abstract

ABSTRACT1. Crunoecia irrorata is widely dispersed across Europe, but rare and red-listed in Finland. Its geographical range comprises most of the southern boreal zone in Fennoscandia. The species is confined to springs in the north, but occurs also in lower reaches of headwater streams in central and western Europe. It becomes more rare and less abundant towards the limits of its range across Europe, showing diffusive rarity. Glacial history and climate limit the distribution of the species in the north.2. The most important habitat characteristic for C. irrorata in Finland was the total area of helocrene habitats. Its occurrence was positively related to taxon richness of benthic macroinvertebrates, but not bryophytes. Co-occurrence of C. irrorata with other red-listed springdependent taxa was observed, indicating high conservation value of the springs occupied.3. Crunoecia irrorata occurred frequently in moderately disturbed springs, indicating tolerance to human disturbance around springs. However, the effect of the disturbance on population size is not known. Forestry and water and gravel extraction are potential threats to C. irrorata, and only a few of its populations are strictly protected. Therefore, populations of C. irrorata in the boreal zone should be conserved and monitored to ensure the species' survival at the northern limits of its range.

The environmental requirements of Crunoecia irrorata (Curtis, 1834) (Trichoptera: Lepidostomatidae) and the potential of the species for use as an indicator: an example from the Vistulian glaciation area

“…Our results slightly support the observation that C. irrorata prefers higher pH values (Ilmonen, 2008) and lower values of water hardness (Schindler, 2004). However, based on currently available results, the relatively weak differences, although statistically significant, of these and several other components (e.g., EC, Si, Mg, Na, and K) between springs with and without C. irrorata in our study area do not permit these components to be used as predictive factors for the occurrence of this species.…”

“…It has been shown that C. irrorata is strongly associated with natural and near-natural springs (Schindler, 2004;Martin and Brunke, 2012), thus serving as an indicator of nearly undisturbed habitat conditions. Additionally, a higher species richness, as well as a higher number of red-listed species, have been reported from springs occupied by C. irrorata compared with springs without this species (Buczyńska, 2008;Ilmonen, 2008). This information also suggests the great potential of this species in terms of the conservation of the co-occurring rare crenic specialists.…”

“…A brief comparison with the average long-term air temperatures in the principal cities of these regions (western: 8.9°C, central and south-eastern: 8.4°C, northeastern: 7.6°C) (http://www.pogodynka.pl/polska/daneklimatyczne/) generally supports this hypothesis at the national scale. However, the frequency values of 42% from the region of Finland (Ilmonen, 2008), with average annual air temperatures of approximately 4°C (Pirinen et al, 2012), contradict the hypothesis. Therefore, our interpretation should be treated with caution because it requires detailed faunistic knowledge of the species to provide a firm basis for testing the hypothesis of a climate-related effect.…”

“…However, based on currently available results, the relatively weak differences, although statistically significant, of these and several other components (e.g., EC, Si, Mg, Na, and K) between springs with and without C. irrorata in our study area do not permit these components to be used as predictive factors for the occurrence of this species. It appears that other morphological characteristics, such as the total area and minerogenic area associated with brooks (Ilmonen, 2008), as well as the occurrence of surrounding deciduous vegetation in association with specific and more diverse substrate types (Hahn, 2000;Schindler, 2004), are more important factors. In this context, Czachorowski (1999) specified helorheocrenes as the general habitat of C. irrorata in Poland.…”

Regional and local drivers of macroinvertebrate assemblages in boreal springs

“…On the other hand, the specific environmental conditions of springs favour the occurrence of several specialized and regionally restricted species (Di Sabatino et al. , 2003; Ilmonen, 2008).…”