Seventy-five Years of Changes in Mallard-Black Duck Ratios in Eastern North America
01 Jan 1976-
About: The article was published on 1976-01-01 and is currently open access. It has received 32 citations till now.
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TL;DR: In this paper, the authors evaluated available data on the role of NIS in marine and estuarine communities and their interactions with other anthropogenic stressors, using an intensive analysis of the Chesapeake Bay region as a case study.
Abstract: Invasions by non-indigenous species (NIS) are recognized as important stressors of many communities throughout the world. Here, we evaluated available data on the role of NIS in marine and estuarine communities and their interactions with other anthropogenic stressors, using an intensive analysis of the Chesapeake Bay region as a case study. First, we reviewed the reported ecological impacts of 196 species that occur in tidal waters of the bay, including species that are known invaders as well as some that are cryptogenic (i.e., of uncertain origin). Second, we compared the impacts reported in and out of the bay region for the same 54 species of plants and fish from this group that regularly occur in the region’s tidal waters. Third, we assessed the evidence for interaction in the distribution or performance of these 54 plant and fish species within the bay and other stressors. Of the 196 known and possible NIS, 39 (20%) were thought to have some significant impact on a resident population, community, habitat, or process within the bay region. However, quantitative data on impacts were found for only 12 of the 39, representing 31% of this group and 6% of all 196 species surveyed. The patterns of reported impacts in the bay for plants and fish were nearly identical: 29% were reported to have significant impacts, but quantitative impact data existed for only 7% (4/54) of these species. In contrast, 74% of the same species were reported to have significant impacts outside of the bay, and some quantitative impact data were found for 44% (24/54) of them. Although it appears that 20% of the plant and fish species in our analysis may have significant impacts in the bay region based upon impacts measured elsewhere, we suggest that studies outside the region cannot reliably predict such impacts. We surmise that quantitative impact measures for individual bays or estuaries generally exist for ,5% of the NIS present, and many of these measures are not particularly informative. Despite the increasing knowledge of marine invasions at many sites, it is evident that we understand little about the full extent and variety of the impacts they create—singly and cumulatively. Given the multiple anthropogenic stressors that overlap with NIS in estuaries, we predict NIS‐stressor interactions play an important role in the pattern and impact of invasions.
396 citations
TL;DR: Overall, the mtDNA data indicate an extremely close evolutionary relationship between Mallards and Black Ducks, and in conjunction with the geographic distributions suggest that the Black Duck is a recent evolutionary derivative of a more broadly distributed Mallard‐Black ancestor.
Abstract: We assayed restriction site differences in mitochondrial DNA (mtDNA) within and among allopatric populations of the Mallard (Anas platyrhynchos) and the American Black Duck (A. rubripes). The observed mtDNA clones grouped into two phylogenetically distinct arrays that we estimate differ by about 0.8% in nucleotide sequence. Genotypes in one clonal array were present in both species, while genotypes in the other array were seen only in Mallards. In terms of the mtDNA "gene tree," the assayed Mallards exhibit a paraphyletic relationship with respect to Black Ducks, meaning that genealogical separations among some extant haplotypes in the Mallard predate the species separation. Evidence is advanced that this pattern probably resulted from demographically based processes of lineage sorting, rather than recent, secondary introgressive hybridization. However, haplotype frequencies were most similar among conspecific populations, so the Mallard and Black Ducks cluster separately in terms of a population phenogram. The results provide a clear example of the distinction between a gene tree and a population tree, and of the distinction between data analyses that view individuals versus populations as operational taxonomic units (OTUs). Overall, the mtDNA data indicate an extremely close evolutionary relationship between Mallards and Black Ducks, and in conjunction with the geographic distributions suggest that the Black Duck is a recent evolutionary derivative of a more broadly distributed Mallard-Black ancestor.
178 citations
TL;DR: Cladistic analysis of 157 characters of definitive plumages and soft parts, natal plumages, tracheae, and nontracheal skeletons of 59 Anatini provided a phylogenetic hypothesis of high consistency and resolution and indicated that interspecific interfertility is a poor indicator of relationship.
Abstract: ABSTP, Act.--Cladistic analysis of 157 characters of definitive plumages and soft parts, natal plumages, tracheae, and nontracheal skeletons of 59 Anatini (sensu Livezey 1986) provided a phylogenetic hypothesis of high consistency (C! = 0.71, excluding unique autapomorphies) and resolution (tree completely resolved except for two nested trichotomies, a trichotomy within the northern-hemisphere mallards, and the tentative placements of two poorly known species of Anas). Major phylogenetic inferences (lists of three or more taxa are in order of increasing relatedness) include the following: (1) monophyly of the tribe is weakly demonstrated; (2) the tribe comprises three subtribes--Cairineae (Cairina, Pteronetta, Aix), Nettapodeae (Chenonetta, Nettapus), and Anateae (all other genera); (3) subtribe Anateae comprises three "supergenera" (each comprising two genera)--Amazonetta (A. brasiliensis and Callonetta leucophrys), Lophonetta (L. specularioides and Speculanas specularis), and Anas (genera Mareca and Anas); (4) the genus Mareca or wigeons includes ix species--capensis, trepera, falcata, sibilatrix, penelope, and americana; nd (5) the large genus Anas comprises two weakly supported subgroups or cohorts, the first of which includes two subgenera (mallards [Anas] and blue-winged ducks [Spatula]) and the second includes four subgenera (Australasian teal [Nesonetta], pintails [Dafila], Holarctic teal [Querquedula], nd spotted teal [Punanetta]). Other findings include that a sister-relationship exists between Anas sparsa nd other mallards, that subgroups of the "true" mallards are largely congruent with biogeographic subdivisions (northern-hemispheric, African, and South Pacific), that the four species of shoveler are monophyletic, that a sister-relationship between the speckled teals (fiavirostris and andium) and brown pintails (georgica, acuta, and eatoni) exists, and that A. querquedula is the sister-group to the greenwinged teals (formosa, crecca, and carolinensis) and not closely related to the blue-winged ducks. Supplementary data and related theory indicated that (1) interspecific interfertility is a poor indicator of relationship, (2) the phylogenetic species concept provided the most practical definition of terminal taxa, (3) a majority of groups within the Anatini originated in the southern hemisphere, (4) body size, sexual size dimorphism, and egg size are strongly constrained phylogenetically, whereas sexual dichromatism and clutch size are less predictable, (5) biparental attendance of broods is primitive within Anatini, and (6) characters of definitive plumages, natal plumages, tracheae, and skeletons had similar consistencies but attained maximal utility at different levels within the phylogeny, which indicates different rates of character evolution within the tribe. Received 19 July 1990, accepted 4 December 1990.
144 citations
TL;DR: The rapid pace of asymmetrical introgression in pinus mtDNA may be the result of initial invasion of chrysoptera populations by pioneering female pinus and/or an unknown competitive advantage of pinus females and their daughters over chrysptera females.
Abstract: I compared the mtDNA compositions of two adjacent populations of Vermivora chrysoptera (golden-winged warbler) at different stages of transient hybridization with its sister species V. pinus (blue-winged warbler). Pinus mtDNA introgresses asymmetrically and perhaps rapidly into chrysoptera phenotypes without comparable reverse introgression of chrysoptera mtDNA into replacing pinus populations. Pinus mtDNA was virtually fixed (98%) in an actively hybridizing lowland population with varied phenotypes. Pinus mtDNA increased from 27% (n = 11) in 1988 to 70% (n = 10) in 1992 in successive samples of a highland population in the initial stages of hybridization. This population comprised mostly pure and slightly introgressed chrysoptera phenotypes. The rapid pace of asymmetrical introgression may be the result of initial invasion of chrysoptera populations by pioneering female pinus and/or an unknown competitive advantage of pinus females and their daughters over chrysoptera females.
105 citations
TL;DR: 7 wetland categories regarding historical changes in mallard and black duck distributions in southern Ontario were used to examine the hypothesis that mallards first invaded and then replaced black ducks on fertile wetlands.
Abstract: We used Canadian Wildlife Service (CWS) survey data (1971-87) to define 7 wetland categories regarding historical changes in mallard (Arras platyrhynchos) and black duck (A. rubripes) distributions in southern Ontario to examine the hypothesis that mallards first invaded and then replaced black ducks on fertile wetlands. Wetlands were defined as: Mallards 1970's―wetlands where mallards invaded in the 1970's but were never recorded as being used by black ducks; Mallards 1980's-wetlands where mallards invaded in the 1980's but were never recorded as being used by black ducks; Black Ducks Replaced 1970's-wetlands where mallards replaced black ducks in the 1970's; Black Ducks Replaced 1980's-wetlands where mallards replaced black ducks in the 1980's; Mallards/Black Ducks--wetlands that mallards and black ducks coinhabited; Black Ducks Only-wetlands used only by black ducks; and Unused
89 citations
References
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TL;DR: Owing to its much smaller gene pool, the Black Duck is vulnerable to eventual swamping through hybridization and introgression, although the present hybridization rate is sufficiently low as to make this unlikely in the foreseeable future.
Abstract: ASTRACT: Changes in general fall and winter distributions of Mallards and Black Ducks over the past century have resulted in markedly increased sympatric contact during pair formation between these two forms, and have been responsible for increased opportunities for hybridization. Bureau of Sport Fisheries and Wildlife records of hybrids from 34 states indicate a minimal current hybridization rate that is about 4% of the frequency expected on the basis of mating according to mathematical probabilities of chance contact. Thus, hybridization is most frequent where both forms are almost equally abundant, indicating that no reinforcement of differences reducing hybridization in the primary zone of contact is detectable. The primary zone of sympatry has moved eastward approximately 300 miles during the past half century and will almost certainly continue to do so. Owing to its much smaller gene pool, the Black Duck is vulnerable to eventual swamping through hybridization and introgression, although the present hybridization rate is sufficiently low as to make this unlikely in the foreseeable future.
49 citations
"Seventy-five Years of Changes in Ma..." refers result in this paper
...Both of these percentages are higher than estimates published earlier by the senior author (Johnsgard, 1967), but the comparability of such data is made more difficult by the separation of actual hybrids from "pure" Black Duck variants that exhibit a few minor Mallard traits perhaps reflecting…...
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...Shortly thereafter it became possible to compare some of these figures with those obtairled by the U.S. Fish and Wildlife Service, and thus addItional analyses for the period 1960-1964 have been published (Johnsgard, 1967)....
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TL;DR: For example, Johnsgard as discussed by the authors traced the distributional changes of wintering Mallards and Black Ducks in the eastern states from 1900 to the present using data compiled by the Audubon Society's annual Christmas Counts.
Abstract: Through the use of data compiled by the Audubon Society's annual Christmas Counts, an attempt has been made to trace the distributional changes of wintering Mallards and Black Ducks in the eastern states from 1900 to the present. During this period the Black Duck has increased relative to the Mallard in few if any states (the Great Lakes region), whereas the Mallard has increased nearly everywhere else (except in the extreme northeast), particularly in the southern coastal states. Deforestation and changes in land use are suggested as probable reasons for this trend, which is not likely to be reversed. Although several rather spectacular shifts in the distributions of various American species of birds have become evident in recent years, the "colonization" of the eastern states by the Mallard (Anas platyrhynchos) has not been so generally recognized. The magnitude of this range extension has been great nevertheless, and the probable reasons for it have been discussed elsewhere (Johnsgard, 1959, 1961). Concomitant with the increase of the Mallard in the eastern states, the native Black Duck (Anas rubripes) has suffered a decline in numbers, and apparently for some of the same reasons as the Mallard has increased. Since this trend is not likely to be reversed in the future, it will be of interest o follow it carefully and thus possibly to predict the fate of the Black Duck. Wing (1943) became interested in the ratios of Mallards to Black Ducks throughout he eastern states before the range shift was at all apparent, and calculated state ratios for the two forms on the basis of the data provided by the annual Audubon Society Christmas counts for the forty years 1900 to, 1939. He found that the average ratios for that period (which, because of the continuously increasing number of counts, is probably typical of the situation somewhat after the midpoint of 1920) indicated that the zone of equal ratios fell in a northsouth line between Michigan and western Florida. East of this line the Black Duck was markedly dominant over the Mallard and west of it the Mallard was equally dominant. Wing's data are presented in Table I, but they are converted from simple Mallard: Black Duck ratios to the alternative method of calculating the relative percentages of each form in the combined sample. This latter means of presenting ratio data has certain statistical advantages (Hickey, 1957). Arguments supporting the use of these data as unbiased estimates of wintering Mallard and Black Duck populations have been presented elsewhere (Johnsgard, 1959), and so will not be repeated here. To test the possibility that these counts might indicate the degree to which the Mallard has moved eastward in recent years, it was de477 Johnsgard in American Midland Naturalist (October 1961) 66(2). Copyright 1961, University of Notre Dame. Used by permission.
11 citations
"Seventy-five Years of Changes in Ma..." refers background in this paper
...Wing's (1943) summary ofthe first 40 years of Christmas Bird Count data indicated the values of utilizing this source of information long before major changes became apparent, and more recently Johnsgard (1961) summarized the data for the subsequent twodecade period of 1940-1949 and 1950-1959....
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5 citations