Wolf Island Research Articles

Concentrations and loads of metals, nutrients and organic contaminants entering the St. Lawrence River at Wolfe Island, 2000 to 2019

Water quality trends and loads were analyzed at Wolfe Island for the years 2000 to 2019. This station captures the nutrient and contaminant concentrations leaving the Canadian Great Lakes system into the St. Lawrence River. In addition to tracking what is leaving the Great lakes system, this station provides an indication of contaminants flowing downstream where a number of sensitive areas exist such as the Thousand Island National Park as well as the St. Lawrence River Area of Concern at Cornwall. In terms of trends, trace metals and PAHs are generally decreasing at Wolfe Island while the nutrients and major ions are increasing. Organic compounds are more challenging to summarize since the number of non-detects prevented modeling of many or the frequency of analysis was too low to model. In a general sense, there is an overall decreasing trend in the organics and the large number of compounds whose concentrations are below detection levels does signify the very low concentration of these contaminants. A notable change in trend predominantly for the metals was noted around 2010 and is discussed herein. The amount of recent (5 years) exceedances of the most stringent water quality guidelines is lower than the previous study period (only PCBs and phosphorus, PFOS and most likely dieldrin). While there are many additional downstream sources of contaminants after the Wolfe Island station, the reductions observed from this study indicate a lower contribution from the Great Lakes in many cases.

A power storage system planning model for the Wolfe Island wind farm

As one of the alternatives to conventional energy sources, wind power is a fast-growing renewable technology. The intermittent characteristic of wind speed leads to unstable wind power production; therefore, a storage system is typically needed at wind power farms to stabilize the power output. This project aims to develop a power storage system planning model to optimize the power transfer between wind turbines and storage devices on an hourly basis to stabilize power output and maximize annual net earnings. The developed model utilizes the dynamic programming technique, and it is applied to a case study of the Wolfe Island Wind Farm in Ontario, Canada, for the year of 2020. Two scenarios with different power output tolerance considerations (i.e., tolerance ranges based on 6- and 8-hour subperiods) are analyzed to compare the fluctuations of power output and the total net earnings. The optimized number of storage devices is also discussed. The developed model can provide technical support for the design and operation of power storage systems at wind power farms.

Impacts of Coral Growth on Geochemistry: Lessons From the Galápagos Islands

AbstractCoral geochemical climate reconstructions can extend our knowledge of global climate variability and trends over time scales longer than those of instrumental data. However, such reconstructions can be biased by coral growth and skeletal architecture, such as growth troughs, off‐axis corallite orientation, and changing growth direction. This study quantifies the impact of skeletal architecture and growth on geochemistry using measurements of coral skeletal density, extension rate, and calcification rate, and uses these metrics to improve paleoclimate reconstructions. We present paired geochemistry‐density records at Wolf Island, Galápagos, from three Porites lobata corals: two new paired density and geochemistry records from one fossil coral, and new density data from two previously published modern geochemistry records. We categorize each sampling transect used in this record by the quality of its orientation with respect to skeletal architecture. We observe relationships between geochemistry and density that are not detected using extension or calcification rate alone. These density‐geochemistry relationships likely reflect both the response of coral growth to environmental conditions and the nonclimatic impact of skeletal architecture on geochemistry in suboptimal sampling transects. Correlations of density with Sr/Ca, Ba/Ca, and Mg/Ca are consistent with the Rayleigh fractionation model of trace element incorporation into coral skeletons. Removing transects with suboptimal skeletal architecture increases mean reconstructed SST closer to instrumental mean SST, and lowers errors of reconstruction by up to 20%. These results demonstrate the usefulness of coral density data for assessing skeletal architecture and growth when generating coral paleoclimate records.

"Wolf Island: Discovering the Secrets of a Mythic Animal" by L. David Mech and Greg Breining, 2020. [book review

"Wolf Island: Discovering the Secrets of a Mythic Animal" by L. David Mech and Greg Breining, 2020. [book review

Northern Galápagos Corals Reveal Twentieth Century Warming in the Eastern Tropical Pacific

AbstractModels and observations disagree regarding sea surface temperature (SST) trends in the eastern tropical Pacific. We present a new Sr/Ca‐SST record that spans 1940–2010 from two Wolf Island corals (northern Galápagos). Trend analysis of the Wolf record shows significant warming on multiple timescales, which is also present in several other records and gridded instrumental products. Together, these data sets suggest that most of the eastern tropical Pacific has warmed over the twentieth century. In contrast, recent decades have been characterized by warming during boreal spring and summer (especially north of the equator), and subtropical cooling during boreal fall and winter (especially south of the equator). These SST trends are consistent with the effects of radiative forcing, mitigated by cooling due to wind forcing during boreal winter, as well as intensified upwelling and a strengthened Equatorial Undercurrent.

17. The Environmental Policy of Windmills on Amherst and Wolfe Island and Their Indirect Impact on the Environment

The objective of our project is to look at the indirect effects of windmills on Wolfe and Amherst Island on native wildlife as well as a focus on the environmental policy around windmills. The indirect effects of windmills would include topics such as changed species behavior in response to windmills and potential changes in the ecosystem as a response to dead birds/bats (i.e. has there been a surge in mosquito population with less bats around). The policy section would include topics such as assessing windmill related mortalities in ways that underestimate the environmental impact or people assessing the potential environmental impacts of building windmills at times diversity/activity of the native ecosystem is not well represented. We will be in contact with people from the Amherst Island conservation group as a source of information and for potential volunteering opportunities. We will also be going to Wolfe/Amherst Island to talk to the people there about the windmills as well as observing the windmills up close. The goal of this study would be to inform people about the problem with the windmills as well as to identify some issues with how people are currently assessing the environmental impacts of windmills.

13. Mitigating Avian and Bat Mortality at Wolfe Island’s Wind Facility

This research focuses on exploring existing mitigation and modification options in order to develop appropriate recommendations to aid TransAlta Corporation in curbing bird and bat mortalities on Wolfe Island. Since the construction and operation of the Wolfe Island wind facility in Frontenac County, Ontario began in 2008, it has contributed to the deaths of many local and migratory birds and bats. While official tallies of avian and bat mortalities to date vary across reports, environmentalist groups and residents alike have expressed concerns for the safety of these species citing the facility’s position on a migratory route along the eastern end of Lake Ontario as a key point of contention (Bazillauskas, A. & Yatchew, A., 2011; Blackwell, R., 2012; Dierschke, J et al., 2006). In response, the power company behind the project, TransAlta Corporation, has begun conducting its own investigation into the issue and producing bi-annual monitoring reports of mortalities but has made no significant alterations to their turbines (TransAlta Corporation, 2012). As part of an effort to reduce the direct and indirect effects of the Wolfe Island wind facility on migrating bird and bat species, this report aims to assess the suitability for TransAlta corporation of certain mitigation options such as running turbines on a rotating schedule to account for the high traffic periods throughout the year when species are likely to be most at risk and avoiding the continuous lighting which attracts nocturnal species to the towers.

2. Blown Away: the Impact of the Wolfe Island Wind Turbines on Local Bat Populations

This study was undertaken in order to explore the extent of migratory bat fatalities and assess the ecological impact stemming from the Wolfe Island wind facility near Kingston, Ontario. As the Wolfe Island wind project is the second largest wind farm in Canada, our research and proposed solutions may bridge the gap between local interests in reducing bat mortality and maximizing energy production. Additionally, bat populations are critical to local agriculture; increased mortality could lead to significant agricultural losses as well as potential impacts on components of the bats’ food web. First, information will be gathered, through the use of peer-reviewed journal articles and news items to support our project focus, to assess the magnitude of local bat population change following the construction of wind turbines on Wolfe Island. Further, we will explore the consequences of bat population decline on the local Kingston area ecosystem. Lastly, possible realistic solutions will be investigated in order to lessen the environmental impact of the existing wind turbines, and possibly to alter future policy regarding turbine construction and location. Preliminary results will be presented and discussed with the appropriate representatives from local and provincial bodies relevant to wind energy, environmental policy and conservation efforts.

Understanding the Amenity Impacts of Wind Development on an International Border

Wind energy developments are often controversial. Concerns are often raised about negative impacts on local communities, including impacts on property values. Some of these negative impacts may be offset by compensatory payments made by wind developers. Community involvement in the planning and development process may also reduce negative perceptions associated with wind facilities. However, if the development is near a border between municipalities, states, or even countries, it is often the case that one or more jurisdictions will not be involved in the process or receive compensation, but will, nonetheless, face some costs or impacts from the development. We explore exactly this situation at the border between Canada and the United States in the Thousand Islands region where a wind farm is currently operating on the Canadian border island of Wolfe Island. Using a parcel-level hedonic analysis of property sales transactions, we find that properties in New York with a view of and/or in close proximity to the turbines significantly depreciated in value after construction of the turbines while no negative impacts were observed on properties in Ontario. We highlight a number of factors that could contribute to these differences in impacts on property values, which may also explain the variation in results that currently exists in the literature.

Gray Wolf Island by Tracey Neithercott

Gray Wolf Island by Tracey Neithercott

Present diversity of Galápagos leaf-toed geckos (Phyllodactylidae: Phyllodactylus) stems from three independent colonization events

We re-examined the biogeography of the leaf-toed geckos (Phyllodactylus) endemic to the Galápagos Islands by analyzing for the first time samples of P. gilberti, a species endemic to Wolf island, in a phylogenetic framework. Our aim was to test the three-colonizations scenario previously proposed for these lizards and estimate the age of each colonization event. To achieve this we estimated simultaneously a species tree and divergence times with Bayesian methods. Our results supported the three-colonizations scenario. Similar to a previous hypothesis, the species tree obtained here showed that most species of Phyllodactylus are nested in a single clade with an age between 5.49 and 13.8Ma, whereas a second independent colonization corresponding to P. darwini from San Cristóbal island occurred 3.03Ma ago. The species from Wolf island, P. gilberti, stems from a more recent colonization event (0.69Ma). Thus, present diversity of Galápagos leaf-toed geckos stems from three independent, asynchronous colonization events. As with other Galápagos organisms, the Pacific coast of South America seems to be the source for the founders of P. gilberti.

Limited influence of a wind power project submarine cable on a Laurentian Great Lakes fish community

Summary Previous research has identified the generation of electromagnetic fields (EMFs) emanating from renewable energy project transmission cables to be a potential stressor to aquatic communities. In this study, we investigated whether the presence of a high voltage submarine transmission cable affected the spatial pattern and composition of nearshore and offshore fishes at a Laurentian Great Lakes site. The transmission cable investigated in this study runs 7.8 km along the lakebed of Lake Ontario, carrying electricity from the Wolfe Island wind power project to the city of Kingston, Ontario. In autumn of 2011, both nearshore electrofishing and deeper-water fisheries acoustic surveys were conducted along transects at varying distances to the cable. For both habitat types, no detectable effects of the cable on the fish community were found. Local habitat variables, including substrate or depth, were more important in explaining variation in fish density than proximity to the cable. Common species encountered during the surveys were round goby (Neogobius melanostomus) in the nearshore and alewife (Alosa pseudoharengus) in the deeper channel. American eel (Anguilla rostrata), thought to be an electromagnetically sensitive species, was also encountered during the surveys including in close proximity to the cable. More robust impact assessments require sampling fishes before a cable installation, over greater time frames (additional seasons or years), and habitats that support more diverse native assemblages.

Seasonal changes in movements and habitat preferences of the scalloped hammerhead shark (Sphyrna lewini) while refuging near an oceanic island

Movements and habitat preferences of sharks relative to a central location are widely documented for many species; however, the reasons for such behaviors are currently unknown. Do movements vary spatially or temporally or between individuals? Do sharks have seasonal habitat and environmental preferences or simply perform movements at random at any time of the year? To help understand requirements for the designation of critical habitats for an endangered top predator and to develop zoning and management plans for key habitats, we examined vertical and horizontal movements, and determined habitat and environmental preferences of scalloped hammerhead sharks (Sphyrna lewini). We tracked seven hammerheads for 19–96 h at Wolf Island (1.38oN, 91.82oW) between 2007 and 2009 using ultrasonic transmitters with depth and temperature sensors, and we profiled temperature through the water column. Movements of individual hammerheads fell in two classes: constrained (remaining near the island) and dispersive (moving offshore to pelagic environments). The central activity space or kernel off the southeast side of Wolf Island was small and common to most, but the area varied among individuals (mean ± SE 0.25 ± 0.2 km2), not exceeding 0.6 km2 for any of the sharks, and not changing significantly between seasons. In general, hammerheads showed preference for the up-current habitat on the eastern side of Wolf Island in both the warm and cold seasons. However, the depth of sharks varied with season, apparently in response to seasonal changes in the vertical structure of temperature. Hammerheads performed frequent vertical excursions above the thermocline during offshore movements and, in general, were observed to prefer temperatures of 23–26 °C found above the thermocline. At times, though individuals moved into the thermocline and made brief dives below it. Our results provided evidence that hammerheads (1) are highly selective of location (i.e., habitat on up-current side of island) and depth (i.e., top of the thermocline) while refuging, where they may carry out essential activities such as cleaning and thermoregulation, and (2) perform exploratory vertical movements by diving the width of the mixed layer and occasionally diving below the thermocline while moving offshore, most likely for foraging.

Lithological structure of the Galápagos Plume

We have measured Ni, Ca, and Mn in olivine phenocrysts from volcanoes in the Galápagos Archipelago to infer the mantle source lithologies. Results show that peridotite is the dominant source lithology for Fernandina, Floreana, Genovesa, Wolf Island, and Darwin Island. These volcanoes largely characterize the PLUME, WD, FLO, and DUM Nd, Sr, and Pb isotopic endmembers of Harpp and White (2001). Volcan Wolf, Alcedo, Marchena, and Cerro Azul, also produced from the melting of peridotite sources, have isotopic compositions that can be defined by mixing of the four isotopic endmembers. Our analysis suggests that peridotite was present in the sources of the volcanoes covered in this study and therefore is the dominant source lithology of the Galápagos plume. Pyroxenite melting is generally focused in two isotopically distinct domains: Roca Redonda, Volcan Ecuador, and Sierra Negra in the enriched western part of the archipelago and Santiago, Santa Cruz, and Santa Fe in the depleted east. One implication of this finding is that the Western and Eastern Pyroxenite Domains represent two separate bodies of recycled crust within the Galápagos mantle plume. Furthermore, both isotopically enriched and depleted domains of the archipelago were generated from mixtures of peridotite and pyroxenite. This suggests that there is no relationship between the source lithology of the Galápagos plume and its isotopic characteristics. The identification of peridotite‐source melting in volcanoes with isotopic characteristics that have been attributed to recycled crust points to the importance of mixing in OIB genesis, consistent with studies in the Canary Islands.

Hotspots within hotspots? Hammerhead shark movements around Wolf Island, Galapagos Marine Reserve

Are pelagic species such as sharks and tuna distributed homogenously or heterogeneously in the oceans? Large assemblages of these species have been observed at seamounts and offshore islands in the eastern tropical Pacific, which are considered hotspots of pelagic biodiversity. Is the species distribution uniform at these hotspots or do species aggregate at a finer spatial scale at these sites? We employed three techniques to demonstrate that the aggregations of scalloped hammerhead sharks, Sphyrna lewini, and other pelagic species were confined to the southeastern corner of Wolf Island in the Galapagos Marine Reserve. Coded ultrasonic transmitters were placed on individuals at this site and at another aggregation site at Darwin Island, separated from Wolf by 40 km, and they were detected by monitors moored at the southeastern corner of Wolf Island and rarely by monitors deployed at other sites around the island. Hammerhead sharks, carrying depth-sensing continual transmitters, were tracked for two-day periods in a vessel and shown to reside a disproportionately large fraction of their time at the southeastern corner. Visual censuses were carried out seasonally at the eight monitor sites at Wolf Island, recording the abundance of one species of tuna, four species of jacks, and a number of other species. The highest diversity and abundance of these species occurred in the southeastern corner of the island. Our results support the use of hammerhead sharks as indicator and umbrella species for pelagic hotspots on a fine scale.

Constructing Lithuania: Ethnic Mapping in Tsarist Russia, ca. 1800–1914 by Vytautas Petronis (review)

399 Ab Imperio, 3/2010 “Грозный”), и публикации источ- ников (запись Василия Шуйского 1606 г. и русско-польский договор августа 1610 г., опубликованные в английском переводе по русской публикации начала XIX в. Р. Хел- ли), и гендерные исследования (очерк Даниэля Кайзера (Daniel H. Kaiser) о завещаниях москвичек “третьего сословия” XVIII века) и т.д. Взятые вместе, они если и не меняют радикально наших представлений о русской истории (большинство авторов, что впол- не естественно, выбрало темы, к которым уже обращались в фундаментальных монографиях), то, по крайней мере, показывают перспективность и многообразие подходов, существующих в со- временной славистике, важность междисциплинарных исследова- ний, потенциал культуральных штудий, а также еще раз убеди- тельно демонстрируют уникаль- ность исследовательской манеры Флайера и его продолжающееся плодотворное влияние на исследо- вания средневековой Московской Руси. Daniel RODRIGUES Vytautas Petronis, Constructing Lithuania: Ethnic Mapping in Tsarist Russia, ca. 1800-1914 (Stockholm: Stockholm University, 2007). 309 pp. (=Stockholm Studies in History, 91; Södertörn Doctoral Dissertations, 21). ISBN: 9-789185445 -79-0.1 During the end of the nineteenth century, the Western Provinces constituted the area of the most intense Polish–Russian rivalry, presenting two different nation-building projects (“Russianness” and “Polishness ”). At that time, what is now modern Lithuania, was a borderland of the Russian Empire. The struggle of Russian authorities to curb the Polish elite’s influence and, at the same time, to integrate this periphery within the territorial core of the Empire dictated a multiplicity of approaches to reshape the ethnic and confessional borders used by both the central and local administration . Vytautas Petronis’s book is a published dissertation that analyses the construction of Lithuania as an “imagined community” through ethnic mapping. His approach pretends to be interdisciplinary (combining history, cartography, and symbolic geography); the stated purpose of 1 See also the review of this title by Steven Seegel, earlier published in: Ab Imperio. 2008. No. 1. Pp. 289-293. 400 Рецензии/Reviews are very helpful for those who intend to analyze ethnic or other kinds of mapping in Russia, and must be at the top of the reading list. The same applies to Kivelson’s book Cartographies of Tsardom: The Land and Its Meanings in SeventeenthCentury Russia (2006),4 published only a year before Petronis’s study, as well as her article Cartography, Autocracy and State Powerlessness (1999).5 Within the field of studies on cartography in conjunction with political and ethnic discourses, another scholar, Jeremy Black, is worth mentioning as the author of some very inspiring books such as Maps and History: Constructing Images of the Past (1997) and Maps and Politics (1997).6 Furthermore, the link between cartography (in this case, ethnic mapping), power and nationalism(s) should be highlighted . Quoting Nailya Tagirova, Existence in a constantly expanding territory dictated the need to find an effective mode of administration for the state and its population. The results to a large his doctoral thesis is to observe the evolution of the ethnic Lithuanian territory on imperial and nationalist maps, and thus to understand the extent to which their appearance and meaning change. In order to achieve this, he based his methodology on archival sources, the historiographical corpus, and, naturally, cartographical analysis. Even a brief overview of the historiography of cartography shows the importance of this topic, in particular , in the dimension of a case study and important references to what is known now as a (new) field of imperial history.2 It should be noted (and Petronis acknowledges this in his work) that several authors, such as Alexei V. Postnikov, Leo Bagrow, Mark Bassin, Rostislav I. Sossa and Valerie Kivelson, among many others, have produced significant work in this field of research. Thus, Bagrow’s A History of the Cartography of Russia (1975) or Postnikov’s Russia in Maps: A History of the Geographical Study and Cartography of the Country (1996)3 2 Novaia imperskaia istoriia postsovetskogo prostranstva / Pod red. S. Glebova, I. Gerasimova , A. Kaplunovskogo. Kazan, 2004. 3 Leo Bagrow. A History of the Cartography of Russia up to 1600. Wolfe Island, Ont., 1975; Alexei Postnikov. Russia in Maps: A History of the Geographical Study and Cartography of the Country. Moscow, 1996. 4 Valerie Kivelson. Cartographies of Tsardom: The Land and its Meanings in Seventeenthcentury Russia. Ithaca, 2006. 5 Valerie Kivelson. Cartography, Autocracy and State Powerlessness: The Uses of Maps in Early Modern Russia // Imago Mundi. 1999. Vol. 55. No. 11. Pp. 83-105. 6 Jeremy Black. Maps and History: Constructing Images of the Past. New Haven, 1997; Idem. Maps and Politics. Chicago, 1997. 401 Ab Imperio, 3/2010 as a whole and the position of Lithuanian lands within it. Consequently, they develop Petronis’s main idea by presenting maps as instruments of national construction independently of their scientific or political orientation. Since the integration of previous Polish-Lithuanian Commonwealth lands into the Russian Empire, the Polish question had been a major problem for Russian rulers. As a...

THE ELIMINATION OF RACCOON RABIES FROM WOLFE ISLAND, ONTARIO: ANIMAL DENSITY AND MOVEMENTS

During 1996 to 1998, an average of 52% to 55% of the raccoon (Procyon lotor) population on Wolfe Island, Ontario was vaccinated against rabies during proactive trap-vaccinate-release (TVR) operations. However, during 1999, the percent of the population vaccinated declined to 39% and an outbreak (6 cases) of raccoon rabies occurred on the island from December 1999 to January 2000. The raccoon population on Wolfe Island declined dramatically (71% reduction) from 1,067 raccoons (mean density = 8.4/km(2) [6.4-12.4, 95% CI]) during 1999 to 305 raccoons (mean density = 2.4/km(2) [0.87-4.1, 95% CI]) in the spring of 2000. Raccoon density immediately following the outbreak was significantly lower in cells with rabies cases, suggesting that rabies had a negative effect on population size. However, raccoon density had doubled by 1 yr following the outbreak. Movement of raccoons on Wolfe Island was as great as 24 km. Male raccoons moved greater distances than females. Movements to surrounding islands were also noted for raccoons ear tagged on Wolfe Island which indicates the island could serve as a focus for greater geographic rabies spread. Point infection control (PIC) during 2000, TVR during 2001-02, and the aerial distribution of Vaccinia-Rabies Glycoprotein (V-RG) baits during 2000 and 2003-05 were used to eliminate rabies from Wolfe Island. No cases have been detected since late January 2000 (to February 2007).

Sexual Size Dimorphism and Morphological Evidence Supporting the Recognition of two Subspecies in the Galápagos Dove

Abstract Abstract Sexual size dimorphism is a conspicuous trait of many wild bird species. Differences in body size between the sexes might reflect selective pressures and trade-offs to optimize performance. Here, we analyze the size dimorphism of the Galápagos Dove (Zenaida galapagoensis) using principal component and discriminant analyses with samples obtained from six islands: Santiago, Santa Fe, Santa Cruz, Española, Genovesa, and Wolf. We also reanalyze published morphological data but also including additional samples from Wolf Island to account for morphological differences among islands. Males were significantly larger than females. Discriminant analyses correctly classified 98% of males and 100% of females, and cross-validation of the model correctly classified 97% of males and 98% of females. We created two sexual size dimorphism indices using wing chord and tarsus as body-size surrogates. Significant differences were found in the sexual size dimorphism index for both measurements among islands. Significant differences in sexual size dimorphism among islands might indicate the role of different selective pressures acting on individual islands (e.g., competition, predation, resources, sexual selection), which might result in life history variation of the species among islands. For the first time, we provide significant morphological evidence supporting the classification of the Galápagos Dove into two subspecies: Z. g. galapagoensis and Z. g. exsul.

SEXUAL SIZE DIMORPHISM AND MORPHOLOGICAL EVIDENCE SUPPORTING THE RECOGNITION OF TWO SUBSPECIES IN THE GALÁPAGOS DOVE

Abstract ABSTRACT Sexual size dimorphism is a conspicuous trait of many wild bird species. Differences in body size between the sexes might reflect selective pressures and trade-offs to optimize performance. Here, we analyze the size dimorphism of the Galapagos Dove (Zenaida galapagoensis) using principal component and discriminant analyses with samples obtained from six islands: Santiago, Santa Fe, Santa Cruz, Espanola, Genovesa, and Wolf. We also reanalyze published morphological data but also including additional samples from Wolf Island to account for morphological differences among islands. Males were significantly larger than females. Discriminant analyses correctly classified 98% of males and 100% of females, and cross-validation of the model correctly classified 97% of males and 98% of females. We created two sexual size dimorphism indices using wing chord and tarsus as body-size surrogates. Significant differences were found in the sexual size dimorphism index for both measurements among islands....

Wolf–Darwin lineament and plume–ridge interaction in northern Galápagos

The Wolf–Darwin Lineament (WDL), located in the northwestern sector of the Galápagos Archipelago, lies between the focus of the Galápagos hot spot and the Galápagos Spreading Center. Consequently, most researchers have attributed its origin to the interaction between the plume and the adjacent ridge. We propose that the WDL is caused only partially by the plume–ridge interaction, and instead that it is primarily the result of tensional stresses emanating from the inside corner of the transform fault at 91°W. An additional factor that amplifies the tension in this region is the oblique orientation of the major transform fault with respect to the Nazca plate's spreading direction. This setting creates a transtensional zone whereby strain is partitioned into strike‐slip motion along the transform and extension throughout the inside corner of the ridge–transform system. The area under tension is magmatic owing to the overlapping effects of the ridge and the Galápagos plume. The extensional model predicts no age‐progressive volcanism, which is supported by observed age relationships. The WDL volcanoes define two distinct chemical groups: lavas erupted south of Wolf Island have compositions similar to those produced along the GSC west of 93°W, while those from the northern WDL resemble GSC lavas from the segment directly north of the lineament. This geographic distribution implies that the WDL is supplied by the same type of plume‐affected mantle as the segment of the GSC that produced the lithosphere underlying the volcanoes. The observed WDL geochemical gradients are consistent with the extension model; the region under tension simply taps hybrid products of mixing at the margins of the subridge convection system and the periphery of the plume. Essentially, the stress field around the transform fault, normally not observable in a typical midocean ridge setting, is illuminated by the presence of melt from the adjacent hot spot.