TY - JOUR

T1 - Niche specialization and functional traits regulate the rarity of charophytes in the Nordic countries

AU - Båstrup-Spohr, Lars

AU - Iversen, Lars Lønsman

AU - Borum, Jens

AU - Sand-Jensen, Kaj

PY - 2015

Y1 - 2015

N2 - 1. Charophytes are benthic macroalgae that live in fresh and brackish waters. Given the historic deterioration oftheir habitats and their competitive inferiority relative to tall rooted plants under eutrophic conditions, it ishypothesized that charophytes are among the most threatened autotrophs. Also, it is expected that charophyteswith generalist niches and functional traits, such as tolerance of a broad salinity range and large height, shouldthrive owing to available habitats and stronger competitive ability.2. These hypotheses were tested comparing the rarity of charophytes in the Nordic countries with otherautotrophs and analysing the relationship to species niche specialization and functional traits. A value on ararity–commonness scale was assigned to each species based on their Red List status. Niche specialization wasevaluated by the Outlying Mean Index using a large Danish dataset while traits were derived from the literature.3. Supporting the hypotheses, 50–87% of charophyte species were Red Listed, which is much greater than forvascular aquatic (30–35%) and terrestrial plants (18–28%). Commonness of charophytes decreased significantlywith niche specialization in separate analyses of brackish and freshwater sites. For brackish water species, the mostinfluential parameter determining species distribution was salinity while for freshwater species, alkalinity, lake sizeand chlorophyll concentration played a major role. Four functional traits: shoot height, salinity tolerance, bulbilproduction and flexible life cycle duration were significantly positively related to commonness.4. In conclusion, charophytes contain a larger fraction of threatened species compared with other groups ofautotrophs. The few common charophytes are generalists tolerant of a wide range of conditions, whilespecialists often have short stature, restricted life cycle variability and are rare in the disturbed contemporarylandscape. It is thus a conservation priority to delineate accurately the environmental conditions preferred bythe threatened species and protect or restore proper habitats.

AB - 1. Charophytes are benthic macroalgae that live in fresh and brackish waters. Given the historic deterioration oftheir habitats and their competitive inferiority relative to tall rooted plants under eutrophic conditions, it ishypothesized that charophytes are among the most threatened autotrophs. Also, it is expected that charophyteswith generalist niches and functional traits, such as tolerance of a broad salinity range and large height, shouldthrive owing to available habitats and stronger competitive ability.2. These hypotheses were tested comparing the rarity of charophytes in the Nordic countries with otherautotrophs and analysing the relationship to species niche specialization and functional traits. A value on ararity–commonness scale was assigned to each species based on their Red List status. Niche specialization wasevaluated by the Outlying Mean Index using a large Danish dataset while traits were derived from the literature.3. Supporting the hypotheses, 50–87% of charophyte species were Red Listed, which is much greater than forvascular aquatic (30–35%) and terrestrial plants (18–28%). Commonness of charophytes decreased significantlywith niche specialization in separate analyses of brackish and freshwater sites. For brackish water species, the mostinfluential parameter determining species distribution was salinity while for freshwater species, alkalinity, lake sizeand chlorophyll concentration played a major role. Four functional traits: shoot height, salinity tolerance, bulbilproduction and flexible life cycle duration were significantly positively related to commonness.4. In conclusion, charophytes contain a larger fraction of threatened species compared with other groups ofautotrophs. The few common charophytes are generalists tolerant of a wide range of conditions, whilespecialists often have short stature, restricted life cycle variability and are rare in the disturbed contemporarylandscape. It is thus a conservation priority to delineate accurately the environmental conditions preferred bythe threatened species and protect or restore proper habitats.

U2 - 10.1002/aqc.2544

DO - 10.1002/aqc.2544

M3 - Journal article

VL - 25

SP - 609

EP - 621

JO - Aquatic Conservation: Marine and Freshwater Ecosystems

JF - Aquatic Conservation: Marine and Freshwater Ecosystems

SN - 1052-7613

IS - 5

ER -