Geographic patterns of lake macrophyte communities and species richness at regional scale

Abstract

Questions Are community composition and species richness of aquatic macrophytes determined primarily by local (habitat heterogeneity and water quality) or regional (climate) patterns at regional scale? Do two macrophyte functional groups (i.e. emergent and submerged macrophytes) respond similarly to local and regional patterns? Are lake macrophytes and explanatory variables geographically structured? Location The US state of Minnesota. Methods The community composition and species richness of aquatic flora was studied using presence–absence data in 454 lakes, covering the entire US state of Minnesota. In addition, community composition and species richness of emergent and submerged macrophytes was investigated separately. Variation partitioning based on partial redundancy analysis and partial linear regression was used to study the relative roles of water quality, habitat heterogeneity, climate and sampling effort in explaining community composition and species richness of lake macrophytes, respectively. Results Macrophyte community composition and species richness (all taxa and two functional groups) were explained by water quality and climate. Alkalinity and total phosphorus were water quality variables that most affected community composition of aquatic flora, and macrophyte species richness decreased with increasing concentrations of these two variables. Maximum temperature of the warmest month and mean annual temperature most affected plant community composition, whereas species richness had a negative relationship with minimum temperature of the coldest month. Most significant explanatory variables (e.g. alkalinity, total phosphorus and temperature) were geographically structured, showing a latitudinal change. Conclusions Community composition and species richness of macrophytes were congruently influenced by regional (climate) and local patterns (water quality) at regional scale. Community composition and species richness of helophytes and submerged macrophytes were equally explained by environmental gradients. The latitudinal change in these most significant environmental variables was related to calcareous soils and intensive agriculture, which were situated in the southern part of the state. Macrophyte species richness showed a reverse latitudinal gradient, which was likely due to high nutrient concentrations in southern latitude lakes. Water quality primarily filters species from the regional species pool, allowing only species tolerating high nutrient concentrations, e.g. invasive plants, to survive at southern latitudes.

Aquatic vegetation in deep lakes: Macrophyte co-occurrence patterns and environmental determinants

“…However, our study lends further support to this evidence and highlights the need for further investigations. Indeed, the majority of both earlier and more recent works on this topic focused predominantly, or even exclusively, on water conditions when analyzing macrophyte patterns, neglecting the potential role of sediment (Kolada, 2010;Alahuhta, 2015;Lukács et al, 2015;Pulido et al, 2015). Furthermore, previous investigations that did analyze the depth distribution of macrophytes often included depth among the environmental determinants tested, thereby limiting the analytical potential of the studies and references therein), or used data mainly from shallow ecosystems (Søndergaard et al, 2013).…”

“…The majority of recent works on the relationship between macrophytes and the environment, which have generally been performed on very large datasets and have thus been characterized by a very marked variance, did not detect any degree of randomness in macrophyte cooccurrence before the role of expected driving factors was tested (Kolada, 2010;Alahuhta, 2015). Our findings in-N o n -c o m m e r c i a l u s e o n l y dicate that not testing these factors may result in a misinterpretation of the determinants of macrophyte co-occurrence patterns as well as of their edaphic determinants.…”

Species richness and taxonomic distinctness of lake macrophytes along environmental gradients in two continents

“…To overcome some of these difficulties in investigating freshwater biodiversity patterns, multiple regions should be investigated simultaneously using the same study approach and identical statistical methods to maintain reliable comparability among the study results Heino, Melo, Siqueira, et al, 2015;Tonkin et al, 2016 Alahuhta, Virtala, et al (2017) showed, using almost identical data to our present study, that land use significantly influenced average water quality niche breadths of lake macrophytes in Finland, Sweden and Wisconsin. The study lakes were randomly selected from a larger database of lakes in Finland and Minnesota (Alahuhta, 2015; to maintain comparability with the lower numbers of study lakes from Sweden and Wisconsin. The number of studied lakes was 50 in Sweden and Wisconsin and 60 in Finland and Minnesota.…”

“…The study lakes were randomly selected from a larger database of lakes in Finland and Minnesota (Alahuhta, 2015; to maintain comparability with the lower numbers of study lakes from Sweden and Wisconsin. Macrophyte survey methods are described in detail for Finland in , for Sweden in Naturv ardsverket (2010), for Minnesota in Alahuhta (2015) and for Wisconsin in Sass et al (2010). Surveys were executed in all the study areas during the growing season Table 1).…”

Indicator Values of Emergent Vegetation in Overgrowing Lakes in Relation to Water and Sediment Chemistry

“…However, this study referred to changes in vegetation patterns in the total covered area, but not in relation to lake area. On the other hand, an increased share of helophytes, typically, is associated with a rise in water trophy in opposition to hydrophytes [8,32].…”