Dataset of Beaver creates early successional hotspots for water beetles Water beetles in Evo 2019 Authors: Petri Nummi, Wenfei Liao, Juliette van der Schoor, John Loehr The dataset was utilised in the paper entitled “Beaver creates early successional hotspots for water beetles” by Petri Nummi, Wenfei Liao, Juliette van der Schoor, John Loehr published on Biodiversity and Conservation 30, 2655–2670 (2021). https://doi.org/10.1007/s10531-021-02213-8 Study sites The data was collected at Evo (61°12′ N, 25°07′ E) in southern Finland. Lakes of this area are oligotrophic, and relatively small (0.1–49.5 ha). All these habitats contain fish. North American beavers (Castor canadensis) inhabit the study area and create flowages by damming existing ponds but they sometimes also dam creeks. Within the landscape, beavers move from one lake to another every three years on average, resulting in abandoning old sites and creating new beaver habitat patches. To study how water beetles responded to beaver-created succession, we selected four types of ponds having five replicates in each category: (1) New Beaver Ponds: newly formed ponds between 2 and 4 years old that have raised water level through damming; (2) Old Beaver Ponds: ponds which beavers may or may not be currently present in, but the beaver constructed dam still functions and maintains a raised water level (7–33 years old); (3) Former Beaver Ponds (Abandoned beaver ponds): with no current beaver presence and which have previously had raised water level due to a beaver constructed dam, but the dam has been breached and the water level has dropped; (4) Never Engineered Ponds: ponds which have not encountered raised water level through beaver damming during the last 50 years. Sampling methods We employed activity traps without bait to sample water beetles. The traps consisted of 1L glass jars with a funnel of 10 cm at the large end and 2.3 cm at the narrow end. At each location, we placed 10 traps approximately 1 m from the shoreline where the water was at least 30 cm of depth. The traps were placed horizontally on the bottom and attached to the surrounding vegetation to keep them in place. We measured the depth of each trap (cm) and estimated the percentage of vegetation of the sampling locations, then we averaged these parameters for each pond. After 48 h, traps were emptied by sieving the content using a sieve with 1 mm mesh. Adult beetles were identified to the species level. Dataset In the dataset (file “Raw_data_Evo_Beaver_water_beetles_2019.xlsx”) are two sheets. The sheet “StudySites” gives basic information on the sampled ponds. The age of beaver ponds and the years of the abandoned ponds are given. The coordinates of all ponds are given. For example, Arabiankorpi locates at 61.2132 N, 25.0928E. The sampling date means the date of traps being retrieved. The sheet “Water_beetle_raw_data” gives all the observations of water beetles from each trap. In total, 26 Dytiscidae species, two Noteridae species, and two Haliplidae species were caught during the trapping. The code of Pond is in line with the sheet “StudySites”. For example, Pond “N1” means the site Arabiankorpi. The code of Trap stands for each trap. For example, “N1.1” means the first trap of New Beaver Pond No.1 (Arabiankorpi). “SpeciesRichness” means the species richness of all water beetle adults in a trap, including Dytiscidae, Noteridae, and Haliplidae in our case. “Abundance” means the abundance of all water beetle adults in a trap. “Type” means the categories of the ponds. “NEW” means new beaver ponds; “OLD” means old beaver ponds; “ABANDONED” means former beaver ponds; “NEVER” means never engineered ponds.

2023