Population genomics indicate three different modes of divergence and speciation with gene flow in the green-winged teal duck complex

The processes leading to divergence and speciation can differ broadly among taxa with different life histories. We examine these processes in a small clade of ducks with historically uncertain relationships and species limits. The green-winged teal (Anas crecca) complex is a Holarctic species of dabbling duck currently categorized as three subspecies (Anas crecca crecca, A. c. nimia, and A. c. carolinensis) with a close relative, the yellow-billed teal (Anas flavirostris) from South America. We examined divergence and speciation patterns in this group, determining their phylogenetic relationships and the presence and levels of gene flow among lineages using both mitochondrial and genome-wide nuclear DNA obtained from 1,393 ultraconserved element (UCE) loci. Phylogenetic relationships using nuclear DNA among these taxa showed A. c. crecca, A. c. nimia, and A. c. carolinensis clustering together to form one polytomous clade, with A. flavirostris sister to this clade. This relationship can be summarized as (crecca, nimia, carolinensis)(flavirostris). However, whole mitogenomes revealed a different phylogeny: (crecca, nimia)(carolinensis, flavirostris). The best demographic model for key pairwise comparisons supported divergence with gene flow as the probable speciation mechanism in all three contrasts (crecca−nimia, crecca−carolinensis, and carolinensis−flavirostris). Given prior work, gene flow was expected among the Holarctic taxa, but gene flow between North American carolinensis and South American flavirostris (M ~0.1 - 0.4 individuals/generation), albeit low, was not expected. Three geographically oriented modes of divergence are likely involved in the diversification of this complex: heteropatric (crecca−nimia), parapatric (crecca−carolinensis), and (mostly) allopatric (carolinensis−flavirostris). Ultraconserved elements are a powerful tool for simultaneously studying systematics and population genomics in systems like this.

Does invasive common reed in coastal salt marshes impact dabbling duck food availability?

Common reed, Phragmites australis , a non-native perennial grass, is considered a nuisance species to land managers and wildlife biologists. Common reed thrives in areas with reduced soil salinities, increased nitrogen availability, and anthropogenic shoreline development. The expansion of non-native common reed into tidal wetlands of North America detrimentally affects native wildlife by altering resource utilization, modifying trophic structures, and changing disturbance regimes. Thus, it also has the potential to drastically affect dabbling duck energetic carrying capacity in salt marsh ecosystems. We assessed whether invaded monocultures of common reed in dabbling duck habitat could alter the availability of invertebrate and seed foods for the mallard [ Anas platyrhynchos ], American black duck [ Anas rubripes ], green-winged teal [ Anas crecca ], northern shoveler [ Spatula clypeata ], and northern pintail [ Anas acuta ] as compared to wetland type (mudflat, low marsh, high marsh, and impoundments). We compared food and energy availability in >90% common reed monocultures to non-common reed invaded saltmarshes in five study areas in Edwin B. Forsythe National Wildlife Refuge, New Jersey, 2015–16 . To estimate wetland specific food energy supply, we collected sediment core samples, fixed with formalin, washed, dried, sorted, and weighed for seeds and invertebrates. We multiplied biomass (g) by True Metabolizable Energy values to estimate species-specific dabbling duck food energy availability. We further estimated wetland specific energetic carrying capacity (duck-energy-days) based on known species-specific energetic demands. We determined that duck-energy-days/ha were greater for dabbling ducks in wetlands invaded with common reed because they contained more consumable seed energy and less consumable invertebrate energy. However, future research should explore how accessible these foods are if common reed grass is too dense. To aid in restoration efforts once common reed is removed by control efforts, our results indicate a robust seed bank exists in the soil strata thus increasing salt marsh seed biodiversity.

Effect of Habitat Management on Duck Behavior and Distribution During Spring Migration in Indiana

Spring migration is an important life stage for ducks because their ability to find and acquire nutrients can affect subsequent reproductive success. Therefore, providing sufficient habitat to support the energetic needs of ducks and facilitate efficient feeding is a goal of habitat management and restoration. The rapid, unpredictable flood events that regularly occur in highly modified landscapes can make habitat management challenging and justify diverse management strategies. We examined the effect of habitat management on dabbling duck behavior and distribution during spring migration in southwest Indiana. We investigated three management options for wetlands: active management, passive management, and unmanaged agricultural food plots. We assessed duck behavior and density on 14 wetlands at Patoka River National Wildlife Refuge and Management Area. The agricultural food-plot areas had the lowest estimates of food availability followed by the actively managed areas; the passively managed wetlands had the greatest estimate. Dabbling duck density was greatest on the actively managed wetlands followed by food plots coming in second and passively managed wetlands third. Most dabbling ducks fed more intensively while on the passively managed wetlands followed by the actively managed and food-plot wetlands. Conservation prioritization of passively managed areas would provide larger areas for dabbling ducks to feed, but active management provides habitat regardless of climatic variability. Moving forward, wetland complexes encompassing diverse wetland management approaches would be the best option for spring-migrating waterfowl as these complexes can provide high-quality habitats and buffer against uncontrollable climactic conditions.

Sarcocystis rileyi in UK free-living wildfowl (Anatidae): surveillance, histopathology and first molecular characterisation

BackgroundReports from UK hunters of ‘rice grains’ in muscles of shot wildfowl (Anatidae) coincided temporally with the finding of sarcocystosis in a number of ducks found as part of the Wildfowl & Wetlands Trust long-term general surveillance of found dead waterbirds. Sarcocystis rileyi has also been relatively recently confirmed in wildfowl in north-eastern Europe.MethodsThis study uses four approaches to investigate UK wildfowl sarcocystosis: first, through a hunter questionnaire that captured historical case data; secondly, through an online reporting system; thirdly, DNA sequencing to characterise UK cases; and fourthly, histological myopathy assessment of infected pectoral muscle.ResultsOur questionnaire results suggest Sarcocystis infection is widely distributed throughout the UK and observed in 10 Anatidae species, reported cases increased since the 2010/2011 shooting season, with the online reporting system reflecting this increase. DNA sequencing (18S rRNA gene and internal transcribed spacer-1 region) of UK isolates confirmed S rileyi in the five dabbling duck host species tested and the associated histopathological myopathy is described.ConclusionThis work highlights an emerging issue to European wildfowl species and provides much opportunity for further research, including the impacts of S rileyi and the described myopathy on host health, fitness and survival.

Moving at the speed of flight: dabbling duck-movement rates and the relationship with electronic tracking interval

Context Effective wildlife management requires information on habitat and resource needs, which can be estimated with movement information and modelling energetics. One necessary component of avian models is flight speeds at multiple temporal scales. Technology has limited the ability to accurately assess flight speeds, leading to estimates of questionable accuracy, many of which have not been updated in almost a century. Aims We aimed to update flight speeds of ducks, and differentiate between migratory and non-migratory flight speeds, a detail that was unclear in previous estimates. We also analysed the difference in speeds of migratory and non-migratory flights, and quantified how data collected at different temporal intervals affected estimates of flight speed. Methods We tracked six California dabbling duck species with high spatio-temporal resolution GPS–GSM transmitters, calculated speeds of different flight types, and modelled how estimates varied by flight and data interval (30min to 6h). Key results Median migratory speeds were faster (but non-significant) for the larger mallard (Anas platyrhynchos; 82.5kmh–1), northern pintail (Anas acuta; 79.0kmh–1) and gadwall (Mareca strepera; 70.6kmh–1), than the smaller-bodied northern shoveler (Spatula clypeata; 65.7kmh–1), cinnamon teal (Spatula cyanoptera; 63.5kmh–1) and American wigeon (Mareca Americana; 52kmh–1). Migratory flights were faster than non-migratory flights for all species and speeds were consistently slower with an increasing data interval. Implications The need to balance time and energy requirements may drive different speeds for migratory and non-migratory flights. Lower speeds at longer intervals are likely to be due to a greater proportion of ‘loafing’ time included in flighted segments, demonstrating that data acquired at different intervals provide a means to evaluate and estimate behaviours that influence speed estimation. Shorter-interval data should be the most accurate, but longer-interval data may be easier to collect over lengthier timeframes, so it may be expedient to trade-off a degree of accuracy in broad-scale studies for the larger dataset. Our updated flight speeds for dabbling duck species can be used to parameterise and validate energetics models, guide management decisions regarding optimal habitat distribution, and, ultimately, improve conservation management of wetlands for waterfowl.

Dna barcoding, population genetics, and phylogenetics of the illegally hunted Philippine Duck Anas luzonica (Aves: Anseriformes: Anatidae)

DNA barcoding is extensively used as a species identification and delineation tool. The aim of this study was to generate a barcode profile for mitochondrial cytochrome c oxidase subunit 1 (COI) in the Philippine Duck Anas luzonica, a dabbling duck species endemic to the Philippines that is classified as ‘Vulnerable’ by the International Union for Conservation of Nature (BirdLife International 2016). COI barcodes were successfully obtained using muscle tissue samples from 46 A. luzonica individuals confiscated from illegal hunters in Pantabangan, Nueva Ecija. Analysis of TrN+Γ+I distances among the Anas luzonica COI sequences and those of 25 other Anas species revealed that COI barcodes cannot generally delineate hybridizing species. While Anas luzonica was differentiated from other species it is known to hybridize with and formed a monophyletic group in the neighbor-joining tree generated, sampling from areas of sympatry is needed since individuals were obtained from only one sampling site. The population structure of the Anas luzonica population was also examined using mitochondrial DNA control region and COI sequences. The population had high haplotype diversity and low nucleotide diversity, an indication that a bottleneck event had occurred, which is likely due to extreme hunting pressures and habitat destruction. The population under study exhibited high genetic diversity. Given that the samples for this study came from a single locality, sampling from other localities is required to determine whether other populations are facing the risk of reduced fitness (inbreeding depression).

Evaluating the relationship between local food availability and wetland landscape structure in determining dabbling duck habitat use during spring migration

Wetlands in the Nebraska's Rainwater Basin (RWB) have decreased by 90 percent over the past two centuries and are subject to on-going degradation of quality from urban and agricultural land-use practices. Losses in wetland habitat quantity and quality are important because the RWB serves as a critical spring staging area to [about]7 million dabbling ducks, including approximately 50 percent of North America's mid-continent mallard (Anas platyrhynchos) population, and 30 percent of North America's total Northern pintail (A. acuta) population. During spring, waterfowl depend on wetland habitat for aquatic invertebrates and plant materials to accumulate the energy and protein needed to complete migration and initiate egg production. If demands for quality food resources are not met, waterfowl may arrive at breeding grounds in poorer body condition, and consequently be less likely to achieve reproductive success. This cross-seasonal effect is believed to be driven by excessive habitat loss at mid-latitudes, introduction of invasive plant species, and depletion of food resources by fall migrants. Given the importance of food resource acquisition at mid-latitude stopover sites and subsequent effects on recruitment, the goal of this study was to improve understanding of food resource availability in wetlands and the relationship to habitat use by spring-migrating waterfowl. I conducted weekly waterfowl surveys and quantified local habitat characteristics including seed density (kg/ha), invertebrate density (kg/ha), energy derived from food resources (kcal/ha), water depth, wetland area, vegetative cover, and several water quality parameters at 32 wetlands in spring 2014 and 35 wetlands in spring 2015. Additionally, I quantified wetland habitat surrounding each study site by assessing wetland area and number of wetlands (greater than 1ha) within 2.5km and 5km of a study site. Study sites were located on public lands managed by the Nebraska Game and Parks Commission and the U. S. Fish and Wildlife Service, private conservation easement lands enrolled in the Wetlands Reserve Program (WRP), and on private lands managed for agriculture (cropped and non-cropped). A set of species distribution models were developed to explain spring dabbling duck density and species richness in the RWB. I hypothesized that a combination of local (food density, energy, water depth, wetland area, and vegetative cover) and landscape variables would explain the greatest amount of variability in dabbling duck density. In 2014 (a dry year), energy, seed density, water depth, wetland area, and wetland density in the surrounding landscape were positively associated with dabbling duck density; however, invertebrate density and vegetative cover had no influence on dabbling duck density. In 2015 (wet year), seed density and energy were positively associated with dabbling duck density; however, water depth, wetland area, vegetative cover, invertebrate density, and wetland area in the surrounding landscape had no influence on dabbling duck density. Wetland area and water depth were the only useful explanatory variables for explaining species richness in 2014, whereas in 2015 dabbling duck species richness was best explained by wetland area and vegetative cover. I used non-parametric analyses to compare seed density, and true metabolizable energy (TME) at three wetland types; public, WRP, and cropped wetlands. Seed density did not vary among wetland types in 2014 or 2015. Median seed density estimates during both years at public, WRP, and cropped wetlands were 593kg/ha (x = 621kg/ha), 561kg/ha (x = 566kg/ha), and 419kg/ha (x = 608kg/ha) respectively. Seed density was consistent between years for public and WRP wetlands, but varied between years for cropped units (p less than 0.05). Variation in seed density between years at cropped wetlands was likely influenced by the presence/absence of agricultural waste grains. Cumulative TME varied among wetland type in 2014 and 2015, with greater TME at cropped wetlands (median = 2431kcal/kg) than public (median = 1740kcal/kg) and WRP wetlands (median = 1781kcal/kg), however TME did not differ between WRP and public wetlands. TME was consistent among wetland types between 2014 and 2015. Seed density estimates from this study were statistically greater than estimates currently used for management planning in the RWB, however, TME estimates were statistically less than estimates currently assumed for WRP and public wetlands in the region. My estimates for mean aquatic invertebrate density were approximately 40-fold less than estimates for mean seed density. Benthic communities accounted for 68 percent of the total invertebrate density, however invertebrate diversity was greater in nektonic communities. Neonicotinoid synthetic insecticides are believed to have a deleterious effect on aquatic invertebrate communities in agricultural areas, although their occurrence in RWB wetlands were previously unknown. I detected trace levels of neonicotinoids in 92 percent of water samples collected in wetlands sampled in the RWB during the spring of 2015. I predicted a relatively high detection rate given the intensity of row crop production in the region, though concentrations were lower than expected. Concentrations at 26 wetlands sampled fell below toxicity benchmarks proposed by the Canadian Environmental Quality Guidelines, and only 11 percent of wetlands sampled had concentrations exceeding the most conservative benchmark proposed by the Environmental Protection Agency. Neonicotinoids concentrations were minimal at wetlands with vegetative buffers strips greater than or equal to 50m between a wetland and a cropped field, relative to wetlands with vegetative buffers strips less than 50m. Although neonicotinoid levels were below lethal concentrations for all aquatic invertebrates identified in this study, I observed a negative association between neonicotinoid concentrations and aquatic invertebrate density (g/m2).

Hybridization between the Mallard and native dabbling ducks: causes, consequences and management.

Waterbirds are currently facing various threats throughout the world. One threat that is often overlooked is hybridization with introduced species. This threatening process is especially significant for dabbling ducks (Genus Anas). The Mallard (Anas platyrhynchos) has been introduced to various parts of the world and now hybridizes and threatens numerous Anas species. In this paper, we review hybridization between Mallards and dabbling ducks with a specific emphasis on threats to the Pacific Black Duck (A. superciliosa). We then present an overview of the potential mechanisms of hybridization and discuss monitoring techniques. We conclude by proposing management strategies and speculating on the future of native dabbling duck species.