Habitat background selection by colonizing intermittent pond invertebrates

Abstract

Habitat selection processes by organisms colonizing freshwater bodies have not been commonly studied, despite their obvious relevance to wetland ecology and management. We monitored, weekly, all organisms that appeared in tanks with different backgrounds (brown; white) and substrate/food availability treatments (control; added leaf litter; added algae) floating on the water surface of a natural intermittent pond. The experiment lasted for 14 weeks, from pond filling to pond drying, during which time we collected around 9,000 colonizing insects per m 2 (e.g., Diptera, Coleoptera, Hemiptera, and eggs) and a similar number of colonizing non-insects (e.g., Acari, Crustacea, Gastropoda, and ephippia). Non-insects exhibited greatest colonization early in the hydroperiod, correlated with major rain-fall events. Insect colonization was low at first, peaked in late May, and thereafter remained high until the pond dried. Most ovipositing female insects (especially chironomids) were attracted to tanks with a dark background or those containing decomposing dark leaves, although there were exceptions related to taxon (e.g., beetles) and hydroperiod. Non-insects showed treatment preferences similar to the insects, with cladoceran ephippia appearing more in the Leaf treatment. Colonization mechanisms were deemed 'active' for insects and largely 'passive' for the microcrustaceans, and the various possibilities for the latter (heavy rainfall, wind, wildlife) are discussed. For highly dispersive taxa, such as adults of the beetles Helophorus sp. and Anacaena sp. colonization densities at the pond surface were calculated to attain maxima of around 26 and 33 m -2 respectively, in early May.

Ecological Drivers of Cladoceran Diversity in the Central European City (Łódź, Poland): Effects of Urbanisation and Size of the Waterbody

“…The key characteristic driving the harsh physicochemical environment is the cyclical drying and re-wetting of the pond basin (hydroperiodicity) (Vanschoenwinkel et al, 2009;Williams, 1996). The fluctuating hydroperiod causes a reduction in habitat volume during drying, increased insolation and temperature, large fluctuations of pH and conductivity, and reduced dissolved oxygen concentrations (turbidity, nutrient levels and trophic processes will all be influenced by the physicochemical processes occurring within ephemeral ponds) (Williams, 1996;Williams, 2006).…”

“…As a result of the extreme physicochemical demands (caused by the cyclical drying and re-wetting of the pond basin -hydroperiodicity) on flora and fauna, "constraint" and "restriction" are common misconceptions regarding ephemeral pond biodiversity (Williams, 1996). Adaptation to the demanding conditions within ephemeral ponds has enabled a relatively diverse and unique ecology to inhabit them (Williams, 2006). Macroinvertebrates are the largest group recorded in ephemeral ponds (Zacharias et al, 2007), although microcrustacea are also very well represented (Khalaf and MacDonald, 1975).…”

“…The Gastropoda Anisus leucostoma, and Odonata species Aeshna juncea and Libellula quadrimaculata exhibit a diapause state during dry periods (Nicolet et al, 2004). A number of invertebrate taxa lay eggs with variable diapause characteristics (bet hedging): some hatch after the initial inundation, but some will only respond to a later inundation to raise the chance of maintaining a successful population within the ephemeral pond (Simovich and Hathaway, 1997;Williams, 2006). Diapause can be maintained across many time scales, from for one season, to years or even decades (Hairston, 1996).…”

“…The Lowland Pond Survey 1996 estimated UK pond numbers to be only 228,900. Between 1984 and 1990 the loss of small ponds in the UK was estimated to be between 4-9% (Williams, 2006). Documented pond loss in different UK regions is presented in Table 2.5.…”

“…Adequate management of these systems will only become a reality if ephemeral ponds are recognised as a valuable environment for rare flora and fauna (Williams, 1997;Biggs et al, 2001). The value of ephemeral ponds needs to be disseminated to the public to increase public knowledge and their status (Williams, 2006;Zacharias et al, 2007). Regional and national biodiversity assessment and monitoring should consider ephemeral ponds to encompass the whole range of aquatic environments (Nicolet et al, 2004).…”