Pond Complex Research Articles

Modelling Water Depth, Turbidity and Chlorophyll Using Airborne Hyperspectral Remote Sensing in a Restored Pond Complex of Doñana National Park (Spain)

Restored wetlands should be closely monitored to fully evaluate the effectiveness of restoration efforts. However, regular post-restoration monitoring can be time-consuming and expensive, and is often absent or inadequate. Satellite and airborne remote sensing systems have proven to be cost-effective tools in many fields, but they have not been widely used to monitor ecological restoration. This study assessed the potential of airborne hyperspectral remote sensing to monitor water mass characteristics of experimental temporary ponds in the Mediterranean region. These ponds were created during marsh restoration in Doñana National Park (south-west Spain). We used hyperspectral images acquired by the CASI-1500 hyperspectral airborne sensor to estimate and map water depth, turbidity and chlorophyll a in a subset of the 96 new ponds. The high spatial and spectral resolution of the CASI sensor allowed us to detect differences between ponds in water depth, turbidity and chlorophyll a, providing accurate mapping of these three variables, and a useful method to assess restoration success. High levels of spatial variation were recorded between different ponds, which likely generates high diversity in the animal and plant species that they contain. These results highlight the great potential of hyperspectral sensors for the long-term monitoring of wetland complexes in the Mediterranean region and elsewhere.

Large multi-decade beaver ponding changes in the subarctic Hudson Bay Lowlands, Canada observed using satellite remote sensing

Beavers strongly impact hydrology and ecosystems through their widespread dam building that creates ponds and wetlands. Monitoring the relative abundance of beavers and their waterbodies is needed to assess these effects and factors influencing population levels. However, the ability to do this over vast, remote regions is limited with conventional aerial or field-based surveying. To address this challenge, we developed a satellite remote sensing method to track beaver ponding changes over multiple decades and applied it to a 5127 km2 region of the coastal Hudson Bay Lowlands in Manitoba, Canada. Annual, sub-pixel surface water mapping using 30 m resolution Landsat satellite data, combined with a spatial database of beaver dams, permitted the mapping of 37 year (1985–2021) beaver ponding dynamics. We identified 1714 beaver dams and 1085 beaver pond complexes covering 31 km2, indicating that beavers have an important influence on stream hydrology in this high subarctic landscape. The total area of ponding decreased by 53% from 1986–1989 and by 80% by 1995, and then gradually recovered to initial levels by 2015. The early, steep drop in beaver ponding corresponded to a 13% decline in regional surface water area, while a similar wetness decline during 2015–2018 resulted in little change in beaver ponding. We suggest that strong beaver ponding dynamics were likely caused by the interaction between streamflow levels and beaver populations living near their northern range limit and cold tolerance. The pond mapping method can be applied to other regions if the long-term distribution of beaver dams is known, and ponds are large enough to be identified using a Landsat sub-pixel approach.

Assessing biodiversity and regulatory ecosystem services in urban water bodies which serve as aqua-Nature-based Solutions

In sight of a growing urban population and intensified extreme weather events, cities must integrate in their urban planning elements to both reduce their impact (i.e., air and water pollution, degradation of habitats, loss of biodiversity) and increase their resilience to climate change. In contrast to engineering solutions, which normally not only fail to adequately address these issues but often also exacerbate them, Nature-based Solutions are an efficient strategy which can help cities become more sustainable. Aqua-Nature-based Solutions (aNBS) tackle water-related hazards by enhancing water regulation and mitigating flood and drought impacts. However, under a warming climate, aNBS are expected to often dry-out, changing biodiversity and the ecosystem services they support. The aim of this study is to compare the biodiversity of temporarily and permanently wet urban waterbodies which function as aNBS. We selected two pond complexes with different hydroperiod (i.e., different duration, amplitude and frequency of inundation) and studied the riparian vegetation and aquatic macroinvertebrate biodiversity. The Multimetric Macroinvertebrate Index of Flanders was used to determine the macroinvertebrate biodiversity and to assess water quality of the ponds. Using water stable isotopes and piezometers, the hydrological dynamics were studied in order to identify the water regulating ecosystem services these ponds deliver. The results showed that the selected pond complexes have a high plant biodiversity, particularly in temporary ponds. Water quality ranged from moderate to poor and macroinvertebrate biodiversity tended to be greater in permanent ponds. Plant and macroinvertebrate alien species were also found in the aNBS. Regarding water regulating ecosystem services, the pond complexes enhanced infiltration and groundwater recharge, providing resilience to both flooding and drought. Our findings corroborate previous studies on the need of diversifying urban ponds’ hydroperiod to support biodiversity. Thus, integrating well-designed aNBS into urban planning might be a way to make cities more resilient to water climate-related hazards while enhancing biodiversity.

Comparison of nest site selection in Mute Swan Cygnus olor and the expanding Whooper Swan Cygnus cygnus

The warming climate is giving migratory birds new opportunities to extend their breeding ranges. These expansions may have a significant impact on other local bird communities. Here, we investigate the nest site selection of Mute Swan Cygnus olor, and the expanding Whooper Swan Cygnus cygnus. The study aims to assess the differences in habitat use by these two swan species in a lowland anthropogenic landscape. It examines the number of breeding pairs and the surface areas of nesting zones in different habitat types. The field procedures involved the use of unmanned aerial vehicles (UAVs) to survey and locate nests, with geotagged photographs taken to map nest locations. Our results show that Mute Swans primarily occupy oxbows, while Whooper Swans predominantly nest in pond complexes. Moreover, GLM models indicate that Mute Swans tend to choose open areas within a radius of 200 m around the nests, whereas Whooper Swans avoid built-up areas, often choosing forested sites within a radius of 500 m of their nests. These findings suggest that the expansion of the Whooper Swan population has led to changes in the breeding behaviour and habitat use of sympatric Mute Swan populations. The territorial behaviour and aggression of Whooper Swan may be driving Mute Swan away from fishpond habitats. We conclude that interactions between the two swan species are dynamic and have not yet stabilized, so this is an issue that needs to be closely monitored. Understanding these dynamics is essential for the effective conservation and management of wetland habitats in the face of ongoing climate change and shifting breeding ranges of birds.

Thirteen Years of Turtle Capture–Mark–Recapture in a Small Urban Pond Complex in Louisiana, USA

Thirteen Years of Turtle Capture–Mark–Recapture in a Small Urban Pond Complex in Louisiana, USA

Population structure, mate choice, and genome transmission in naturally formed pairs in a Pelophylax lessonae–Pelophylax esculentus hybridogenetic system

Central European water frog Pelophylax esculentus is a hybrid that lives sympatrically and forms genetic systems with one of its parental species, in this case L-E (P. lessonae - P. esculentus). Hybrids are restored in each generation due to hybridogenesis, a unique mode of hemiclonal reproduction. We investigated changes in the species composition, mate choice, and genome transmission in naturally formed pairs in the L-E hybridogenetic system from the Raków fish pond complex (SW Poland). Our observations showed that the genetic system remained the same for over a decade but the share of the taxa and the sex ratios within the species changed. The frequency of P. lessonae decreased by about 20% in favor of P. esculentus. The proportion of males to females of P. lessonae increased twofold and of P. esculentus fourfold. We also found that the stability of the L-E population was ensured by a specific female mate choice pattern with the dominance of homotypic P. lessonae and heterotypic ♀P. esculentus × ♂P. lessonae pairs (almost 90% of the pairs collected from nature). The youngest females and males that formed a successful amplexus were 3 years old. We noted a male-male competition manifested by the exclusion of young males (before the third hibernation) from the participation in the mating. An analysis of genome transmission to gametes revealed that females P. lessonae transmitted Lx, while P. esculentus transmitted the Rx and/or Lx genomes. Males of P. lessonae transmitted the Lx or Ly genomes, while P. esculentus transmitted the Lx, Ly, and/or Rx genomes. The high proportion of the L genomes transferred to gametes enables both the restoration of the parental species P. lessonae and the regular renewal of a new generation of hybrids.Significance statementCentral European water frog complex includes two species: Pelophylax ridibundus (genotype RR) and P. lessonae (LL), and their natural hybrid, P. esculentus (RL). Hybrid individuals of both sexes reproduce due to a specific mode of reproduction, i.e., hybridogenesis, in which hybrids eliminate one of the parental genomes (R or L) from the germ line prior to meiosis and transmit the other one (not recombined, i.e., clonal) to the gametes. The hybrids live in mixed populations with one of the parental species and are restored in each generation. This, in turn, allows a kind of balance to be maintained in a population due to specific mate choice and genome transmission. Our research showed that the stability of the studied population was ensured by female preference to P. lessonae and male-male competition manifested by the exclusion of males under 3 years of age from the participation in the mating.

EFFECT OF COMMERCIAL INORGANIC FERTILIZER ON ABUNDANCE OF PLANKTON IN POND POLYCULTURE SYSTEM

The experiment was conducted to assess and compare the effect of micronutrient enrich commercial inorganic fertilizer and macronutrient enrich traditional inorganic fertilizer on plankton abundance in the manmade earthen ponds of Khulna University pond complex II for a period of three months from August to October 2017. There were three treatments each with three replications. Macro fertilizers (Urea 2.45 g m-1 week-1, TSP 2.45 g m-1 week-1 and molasses–yeast mixture 3.09 g m-1 week-1) were applied in treatment-1 (T1) while commercial inorganic fertilizer (4.5 g m-1 week-1) was applied in treatment-2 (T2) while no fertilizer was applied in treatment-3 (T3). Four different classes of phytoplankton namely Chlorophyceae, Cyanophyceae, Bacillariophyceae, and Euglenophycaea were found in this experiment in which Chlorophyceae (5304.25±223.78 cells L-1) was the dominant class in respect of abundance and number of genera. Additionally, four classes of zooplankton such as Copepoda, Cladocera, Rotifera, Ostracoda were observed in which Copepoda (1559.84±70.48 cells L-1) was the most dominant class in treatment T2 than other treatments. Mean abundance of different phytoplanktons were 8864.77±52.78, 11489.04±295.76, 5983.04±272.88 (cells L-1) in T1, T2 and T3 and mean abundance of zooplankton under treatments T1, T2 and T3 were 3997.65±126.78, 4621.64±45.67, 3017.66 ±137.67 (cells L-1) respectively. The results indicated that mean abundance of phytoplankton and zooplankton were significantly higher (P<0.05) in treatment T2 compared to other treatments. The total mean abundance of plankton was observed significantly higher (P<0.05) in treatment T2 than other treatments. Therefore, it is concluded that micro nutrient rich commercial inorganic fertilizer Bluemix was more effective on the primary production in polyculture ponds as well as increase the production of fish than traditional inorganic fertilizer.

Growth and diet of inanga (Galaxias maculatus) within a small New Zealand coastal pond system

ABSTRACT Inanga (Galaxias maculatus) are found in a range of freshwater habitats around much of the Southern Hemisphere. Although they are reasonably well studied within New Zealand, little is known about the populations found in coastal pond systems. This study focussed on inanga diet and population dynamics within a shallow pond complex in coastal Southland, investigating age, growth, distribution, and diet of juvenile inanga over a spring to autumn period. Otolith analysis indicated a three-month period (September to November) during which fish are hatching, with fish that hatched earlier growing more slowly than later fish. Inanga were found in only one location within the pond complex – a site featuring low water nutrient levels and less access by trout. Diet analysis showed high selectivity for chydorids and chironomid larvae, indicating a mixture of both benthic and pelagic foraging. Overall, this study has provided insight into inanga population dynamics in ponds, which have not previously been observed.

Large methane emission from freshwater aquaculture ponds revealed by long-term eddy covariance observation

Aquaculture ponds are important anthropogenic methane (CH4) sources to the atmosphere. Currently large uncertainties still remain regarding the emission strength of this source type and its relationship with aquacultural farming practices. In this study, the methane flux was measured continuously for four years with eddy covariance (EC) in an aquaculture pond complex in the Yangtze River Delta, China. These ponds have never been dredged and were aerated during part of the aquacultural season. Additionally, floating chambers and inverted funnels were used to investigate spatial heterogeneity of the CH4 flux and to quantify the contribution via ebullition to the flux. The results showed that the daily CH4 flux ranged from 0.1 to 16.7 μg m−2 s−1, with an average value of 4.10 ± 3.08 µg m−2 s−1. Water temperature was the primary driver of the CH4 flux across multiple time scales (half-hourly, daily, and monthly scale). Ebullition was the main transport way accounting for 70% ± 4% of the total CH4 flux. The annual flux in this study was about three times the median flux reported by other researchers for similar freshwater aquaculture ponds. A statistical analysis of our data together with the published flux data reveals that ponds with dredging have much lower CH4 emission flux than those without dredging and suggests that dredging may have a much larger influence on the emission flux than aeration.

Monitoring tidal hydrology in coastal wetlands with the “Mini Buoy”: applications for mangrove restoration

Abstract. Acquiring in situ data of tidal flooding is key for the successful restoration planning of intertidal wetlands such as salt marshes and mangroves. However, monitoring spatially explicit inundation time series and tidal currents can be costly and technically challenging. With the increasing availability of low-cost sensors and data loggers, customized solutions can now be designed to monitor intertidal hydrodynamics with direct applications for restoration and management. In this study, we present the design, calibration, and application of the “Mini Buoy”, a low-cost underwater float containing an acceleration data logger for monitoring tidal inundation characteristics and current velocities derived from single-axis equilibrium acceleration (i.e. logger tilt). The acceleration output of the Mini Buoys was calibrated against water-level and current-velocity data in the hypertidal Bay of Fundy, Canada, and in a tidally reconnected former aquaculture pond complex in North Sumatra, Indonesia. Key parameters, such as submersion time and current velocities during submergence, can be determined over several months using the Mini Buoy. An open-source application was developed to generate ecologically meaningful hydrological information from the Mini Buoy data for mangrove restoration planning. We present this specific SE Asian mangrove restoration application alongside a flexible concept design for the Mini Buoy to be customized for research and management of intertidal wetlands worldwide.

Hydrogeological characteristics of carbonated cretaceous aquifers and their relationship with complexes of collapsed dolines and ponds in Serrania de Cuenca (province of Cuenca, Spain)

The carbonate formations of the cretaceous period of Serrania de Cuenca (Spain), constitute karstified aquifers of great importance and abundant karstic morphologies, both internal (caverns, pit-caves) and external (limestone pavements, collapsed dolines, karst ponds). The lithological variations and the different degree of fracturing and karstification condition the vertical connection of the aquifers, defining irregular aquifer strips of greater secondary porosity that will function as a semi-confined aquifer and that may constitute local aquifers. This influences the hydrodynamic behaviour of the aquifer and main springs and their relationship with karst morphologies, particularly with Cañada del Hoyo pond complex and the so-called “Torcas de los Palancares” collapsed dolines. The study of hydrochemistry and ionic relations evidence the influence of lithology on the chemistry of its groundwater, predominantly calcium and magnesium bicarbonated facies, and the phenomenon of possible disconnection, precipitation and evaporation in the ponds, with bicarbonated magnesium groundwater.

Waterbird Migration through a Saline Wetland in the Western Nevada Desert, USA

A great variety of waterbirds migrate across western Nevada, where places to rest or refuel are nearly non-existent. One exception is a little-known industrial pond complex at the Albemarle U.S., Inc. facility in Silver Peak. In this paper we analyzed 3 years (2014-2016) of near-daily counts to document the timing, abundance, and stopover biology of 73 species traversing one of the driest regions in North America. Average annual bird-use-days exceeded 350,000, of which 93% were contributed by species with affinities to highly saline habitats. Individuals of most species (total estimated 110,000-183,000) passed through within a day or so, although some Ruddy Ducks (Oxyura jamaicensis), Eared Grebes (Podiceps nigricollis) and American Avocets (Recurvirostra americana) made prolonged stays. We treat the most abundant species in detail and show that data from sites that can be monitored daily can complement studies from sites where daily censuses are not feasible. The Silver Peak ponds attract sufficient shorebirds to warrant consideration as a Site of Regional Importance in the Western Hemisphere Shorebird Reserve Network.

ДВУХПРУДОВОЙ НАГУЛЬНО-ВЫРОСТНОЙ РЫБОВОДНЫЙ КОМПЛЕКС

Purpose: development and description of the layout and design solution for a two-pond feeding nursery fish-breeding complex, which characterizes by compact placement of its constituent structures and their adaptation to the topographic conditions of the territory. Materials and methods. The theoretical and empirical basis for the development was made up of well-known recommendations on design and construction of pond complexes and survey data of operating fish-breeding facilities and their structures. During the development, the technologies of search design of engineering projects in compliance with fish breeding requirements and restrictions were used. Results. The fish-breeding complex includes: two fish-breeding ponds with a common dividing dam and a water supply system including a pumping station; water supply pipe system; a system of devices and structures that ensure the release of fish grown in ponds into a fish trap; spillway devices for discharging water from ponds and a fish trap with a set of regulating elements. Fish ponds are located on the floodplain lands of the river Don and are formed by protecting dikes. The bed of the reservoirs is planned with sections with longitudinal and transverse slopes to the water-fish collecting and-transporting ditches arranged in their bottom, allowing them to be emptied and the fish grown in the ponds to be directed to the outlet structures. The release of fish from the ponds is carried out by two tower water outlets. The design of the fish trap provides for the accumulation and seine fishing, it is equipped with means for regulating water discharge and maintaining conditions for fish. Conclusions. The developed layout and design solution for a two-pond fish-breeding complex with one fish trap is adapted to the local relief and the difference in water levels in ponds and in water intake. The implemented layout and design solutions can be used in the development of similar objects

Factors promoting the recolonization of Oahu, Hawaii, by Bristle-thighed Curlews

Suitable habitat for Arctic-breeding migratory shorebirds is decreasing at their traditional wintering islands and atolls in the Central Pacific Flyway (i.e., Oceania) due to habitat degradation, reclamation, and sea-level rise. To maintain the size and resiliency of their populations, migratory shorebirds will need to expand their winter ranges by either colonizing new sites or recolonizing old sites from which they were extirpated. Bristle-thighed Curlews (Numenius tahitiensis) are long-distance migratory shorebirds that breed only in Alaska and winter across a vast region of the Central Pacific, typically on remote, unpopulated islands and atolls. Historically, Bristle-thighed Curlews were considered uncommon transients on the main Hawaiian Islands, but in the mid-1990s, curlews became regular visitors to Oahu and subsequently began wintering at the James Campbell National Wildlife Refuge on Oahu Island in Hawaii. Curlew numbers at this site grew steadily from <5 birds in the mid-1990s to an estimated 126 winter residents (95%CI 108–147) in 2013–2014. Timing of the recolonization event coincided with the establishment of a fenced pond complex that was managed for endangered waterbirds by maintaining areas of shallow water and low vegetation. High rates of apparent annual survival exhibited by adults and subadults (0.86–0.95) confirmed the suitability of the Refuge to curlews. Our results suggest that curlews in Oceania can naturally recolonize wintering islands, a trait that may be key to the survival of this species of conservation concern in an era of rising sea levels.

Trait-Environment Relationship of Aquatic Vegetation in a Tropical Pond Complex System

The relationship between organisms’ traits and the characteristics of their habitats has been a central theme in ecology. Using two complementary approaches to analyze three-matrices of species composition, functional trait, and environment data (RLQ and fourth-corner analyses), we tested if environmental gradient determines aquatic plant traits in ponds in the Pantanal wetland. Furthermore, we tried to understand if plant composition is spatially structured and if environmental gradient is correlated with taxonomic and functional community properties. We sampled aquatic plants coverage in 20 ponds and measured pond size, depth and pH to represent the environmental gradient. We found significant turnover of several traits of aquatic plants along the environmental gradient, being niche partitioning the most probable process structuring plant communities. There was no evidence of spatial autocorrelation determining species composition in the scale of the study, which may indicate that the annual flooding can act as homogenizing factor that promotes species co-occurrence along the ponds. Taxonomic abundance and functional richness were positively related with environmental gradient. Larger and deeper ponds provide higher resource availability thus supporting more functional attributes and vegetation cover. Our results support the hypothesis that niche process is the main driver of aquatic plants in the Pantanal.

The origin and persistence of alpine vernal ponds in mineral soils

AbstractLittle is known of the processes that create and maintain vernal ponds in mineral soils in alpine environments. On the Central Plateau, Tasmania, we tested the hypotheses that vernal pond complexes on mineral soils formed in response to the underlying topography of a glacio‐fluvial plain; relate to present day topography; resulted from past damming by organic accumulation; are moulded by wind. The underlying topography did not relate to the surface ponds, nor were they on steeper slopes than adjacent areas without ponds. The morphology of the ponds and the morphological and edaphic characteristics of the pond complexes and adjacent areas are consistent with an origin by organic material damming. The strongest winds orientate most ponds, rather than the aspect of the slope. Sediments were preferentially caught on sticky traps to the northeast of the ponds, away from fierce prevailing southwesterly winds. Temperature measurements and fortnightly observation showed non‐concordant patterns of variation in water levels in the ponds. We deduce that the complexes of vernal ponds may have formed in previous moister conditions more favourable to organic matter accumulation, possibly in the early Holocene, and are maintained by a faster rate of accumulation of mineral and organic particles in the tussock grassland adjacent to the ponds than in the ponds themselves. © 2019 John Wiley &amp; Sons, Ltd.

Mallards Anas platyrhynchos shot in Eastern Poland: ecological risk evaluated by analysis of trace elements in liver

Mallard Anas platyrhynchos is a numerous and widespread duck of Northern Hemisphere. In some regions, it is an important component of the diet of local inhabitants. It may also serve as an effective bioindicator of pollutions in aquatic environments. In this study, we investigated trace elements concentrations in livers of 23 Mallards shot at fish pond complex during wintering in the Lublin region (SE Poland). The element concentrations followed the pattern: Fe >Mg > Ca > Zn > Cu > Mn > Se > Sr > Cd > Pb > Cr > V > Hg > As > Ni > Sc. Our study revealed lack of sex differences in hepatic element concentrations suggesting similar wintering areas of both sexes. At 8.7% of the examined individuals concentration of Pb was classified as subclinical toxicity or moderate clinical poisoning for Mallards. It indicates serious need for banning of the use of Pb hunting ammunition in those parts of Europe (in that in Poland) where it is still allowed. Such the ban should be established at least in wetlands and waterbodies. Groups of people especially prone to elevated concentration of toxic elements (e.g., pregnant women, children) should avoid consumption of meat originated from wildfowl.

Impacts of Climate Change and Intensive Lesser Snow Goose (Chen caerulescens caerulescens) Activity on Surface Water in High Arctic Pond Complexes

Rapid increases in air temperature in Arctic and subarctic regions are driving significant changes to surface waters. These changes and their impacts are not well understood in sensitive high-Arctic ecosystems. This study explores changes in surface water in the high Arctic pond complexes of western Banks Island, Northwest Territories. Landsat imagery (1985–2015) was used to detect sub-pixel trends in surface water. Comparison of higher resolution aerial photographs (1958) and satellite imagery (2014) quantified changes in the size and distribution of waterbodies. Field sampling investigated factors contributing to the observed changes. The impact of expanding lesser snow goose populations and other biotic or abiotic factors on observed changes in surface water were also investigated using an information theoretic model selection approach. Our analyses show that the pond complexes of western Banks Island lost 7.9% of the surface water that existed in 1985. Drying disproportionately impacted smaller sized waterbodies, indicating that climate is the main driver. Model selection showed that intensive occupation by lesser snow geese was associated with more extensive drying and draining of waterbodies and suggests this intensive habitat use may reduce the resilience of pond complexes to climate warming. Changes in surface water are likely altering permafrost, vegetation, and the utility of these areas for animals and local land-users, and should be investigated further.

Tundra be dammed: Beaver colonization of the Arctic.

Increasing air temperatures are changing the arctic tundra biome. Permafrost is thawing, snow duration is decreasing, shrub vegetation is proliferating, and boreal wildlife is encroaching. Here we present evidence of the recent range expansion of North American beaver (Castor canadensis) into the Arctic, and consider how this ecosystem engineer might reshape the landscape, biodiversity, and ecosystem processes. We developed a remote sensing approach that maps formation and disappearance of ponds associated with beaver activity. Since 1999, 56 new beaver pond complexes were identified, indicating that beavers are colonizing a predominantly tundra region (18,293km2 ) of northwest Alaska. It is unclear how improved tundra stream habitat, population rebound following overtrapping for furs, or other factors are contributing to beaver range expansion. We discuss rates and likely routes of tundra beaver colonization, as well as effects on permafrost, stream ice regimes, and freshwater and riparian habitat. Beaver ponds and associated hydrologic changes are thawing permafrost. Pond formation increases winter water temperatures in the pond and downstream, likely creating new and more varied aquatic habitat, but specific biological implications are unknown. Beavers create dynamic wetlands and are agents of disturbance that may enhance ecosystem responses to warming in the Arctic.

Phylogenetic relatedness of co‐occurring waterbird communities: a test of Darwin's competition‐relatedness hypothesis

The competition–relatedness hypothesis of Darwin states that competition is greater among species that are phylogenetically closely‐related, and such species will tend to appear in separate communities (i.e. the species within communities will be phylogenetically overdispersed). Many studies have tested (and mainly refuted) this hypothesis for plant and bacterial communities. Results for the few studies with avian species are not conclusive. We tested Darwin's hypothesis for waterbirds using a set of open, artificial fish ponds in Doñana, south‐western Spain, that provide relatively homogeneous habitat where competition is likely to be intense. Monthly counts of 38 ponds (for 11 months, i.e. 418 censuses) recorded 76 bird species. Darwin's hypothesis predicted that species appearing in the same pond would be less related phylogenetically than expected if species occurred randomly across ponds and months according to the structure of the overall community across the entire pond complex. However, the waterbird community did not show a predominantly overdispersed pattern, suggesting that interspecific competition among phylogenetically related species was not the main force structuring communities. In contrast, the proportion of clustered communities was higher than expected throughout the annual cycle, indicating that related waterbirds tend to co‐occur on the same site, probably because they have similar microhabitat preferences. Clustering patterns were mainly driven by abundant and closely related duck species, and also by shorebirds. However, few individual pond communities remained significantly different from random after correction for multiple testing. Furthermore, the probability of co‐occurrence of a given species pair was negatively related to the phylogenetic distance between them. In conclusion, our study shows waterbird communities are mainly phylogenetically clustered or random, and do not support the competition‐relatedness hypothesis.