Is the island biogeography model a poor predictor of biodiversity patterns in shallow lakes?

Abstract

1. The classic island biogeography model (IBM) predicts highest species richness in large, connected habitats due to colonisation and reduced risk of extinction. Promoting large, connected habitats has subsequently become a common theme in conservation biology. 2. However, the IBM does not account for direct and indirect interactions among species. For example, planktivorous and benthivorous fish may reduce biodiversity in shallow lakes by inducing shifts to a turbid-water lake state with low habitat complexity. 3. We assessed relationships between species richness, landscape features, fish biomass and lake state in 104 shallow lakes in Minnesota, U.S.A. First, we tested whether lake size and connectivity influenced species richness of fish and biomass of planktivores and benthivores (fish biomass). We subsequently tested whether fish biomass affected the probability that lakes were in turbid versus clear-water states. Finally, we tested whether species richness of macrophytes and taxon richness of aquatic invertebrates showed stronger relationships with lake size and connectivity or with fish biomass and lake state. 4. Fish richness and biomass both increased with lake size and were higher in connected basins. Fish biomass, in turn, increased the probability that lakes would be turbid. In contrast, macrophyte and invertebrate richness were unrelated to lake size or connectivity. Instead, macrophyte richness was best predicted by lake state, while invertebrate richness was predicted by lake state and fish biomass. Richness of both macrophytes and invertebrates was higher in clear lakes, and invertebrate richness was inversely related to fish biomass. 5. Our results indicate the IBM poorly explains the diversity of macrophytes and invertebrates in shallow lakes, with diversity more strongly driven by biotic interactions and influences associated with fish. We suggest that ecological implications of increased connectivity and lake size should be considered in future conservation strategies for shallow lakes.

Lake size and fish diversity determine resource use and trophic position of a top predator in high‐latitude lakes

“…The observed negative relationship between Arctic charr trophic position and lake relative depth is most likely associated with the relatively shallow nature of the largest (>20 km 2 ) study lakes as well as of Datkujavri and Vuolit Spielgajavri (Table S1) where Arctic charr preyed to a great extent upon other fishes. However, the relative importance of lake morphometric characteristics (e.g., area and relative depth) and fish species richness on Arctic charr trophic position and food-chain length is difficult to distinguish because the number of fish species is highly correlated with lake size for our study lakes (Pearson: r = 0.72, P < 0.001) as reported previously (Barbour and Brown 1974;Nolby et al 2015). Comparing energy flow and food-chain length across high-latitude lakes of different size but with single-species fish communities could resolve this issue in the future.…”

“…However, the relative importance of lake morphometric characteristics (e.g., area and relative depth) and fish species richness on Arctic charr trophic position and food-chain length is difficult to distinguish because the number of fish species is highly correlated with lake size for our study lakes (Pearson: r  =   0.72, P  <   0.001) as reported previously (Barbour and Brown 1974; Nolby et al. 2015). Comparing energy flow and food-chain length across high-latitude lakes of different size but with single-species fish communities could resolve this issue in the future.…”

“…Besides affecting the relative importance of littoral and pelagic trophic pathways, lake size may also influence fish species diversity (Barbour and Brown 1974;Nolby et al 2015) and food-chain length in lakes (e.g., Post et al 2000;Takimoto and Post 2013). Increased fish species diversity may lead to substitution of intermediate consumers, but also to increased competition and predation, all of which may induce niche shifts by top predators (cf.…”

Shifts in algal dominance in freshwater experimental ponds across differing levels of macrophytes and nutrients

“…, Nolby et al. ). In the absence of strong fish predation, or potentially in the presence of dense macrophytes, grazer invertebrates can suppress phytoplankton (Bakker et al.…”

“…Increasing macrophyte cover can enable augmented zooplankton biomass through provision of refuges at low to intermediate planktivorous fish densities; however, low macrophyte cover or high fish densities reduce the effectiveness of such refuges (Schriver et al 1995). Thus, greater water clarity is associated with reductions in planktivorous fish through trophic cascades and with reductions in benthivorous fish because of less sediment and nutrient resuspension (Meijer et al 1999, Nolby et al 2015. In the absence of strong fish predation, or potentially in the presence of dense macrophytes, grazer invertebrates can suppress phytoplankton (Bakker et al 2010) and periphyton growth Sayer 2003, Feuchtmayr et al 2009).…”