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Chapter 7: Population Dynamics of the Soft-Shell Clam Mya arenaria
No full textIt is easy to understand in a general way the population dynamics of benthic marine invertebrates, including the soft-shell clam Mya arenaria. To paraphrase Gunnar Thorson (1950), all it takes for a population to maintain itself is for every adult female–male pair to produce two successful larvae over their entire lifetime. But the devil is in the details. The purpose of this chapter is to present some of those details.
Thorson (1950) emphasized the importance of larval supply and settlement in regulating bottom-dwelling invertebrate populations. Yet mid-20th century benthic ecologists focused more on the roles of postsettlement processes involving juveniles and adults in population regulation (Morgan 2001; Underwood and Keough 2001). What controls the population dynamics of Mya arenaria? As I discuss in this chapter, we cannot really say for sure. Or, more accurately, it depends on the place, weather, and year. Increasingly, it depends on the climate. And it certainly depends on what researchers are looking for and how they attempt to measure it. Related questions arise, too. Why does the soft-shell clam live so long, reproduce so many times, and make so many offspring? Why do population sizes vary so widely both spatially and temporally? Why is recruitment successful in some years, but a total bust in other years? How good are population dynamics models at capturing these phenomena? Answers are difficult to find, especially because soft-shell clam populations experience a wide array of environmental conditions in both intertidal and shallow water habitats, with a geographic distribution across multiple continents (Strasser 1998), from warm mid-latitudes (e.g., Hakata Bay, Japan: Goshima 1982; Chesapeake Bay, USA: Kennedy and Mihursky 1971; Pamlico Sound, North Carolina, USA: Skilleter 1994) to polar regions (e.g., Alaska, USA: Powers et al. 2006; White Sea, Russia: Gerasimova et al. 2015). Note, however, that some controversy exists about confusing M. arenaria with other Mya species in Arctic and northwest Pacific regions (Strasser 1998; Zhang et al. 2018).
Detailed reviews of the biology of Mya arenaria, including topics directly related to population dynamics, are presented in other chapters of this book. In this chapter, I review the important processes that affect the abundances of larvae, recruits, juveniles, and adults. I then discuss researchers’ attempts to integrate demographic patterns and build population models. The insights gained from their work may help deepen our understanding of soft-shell clam population dynamics, with implications for management in a rapidly changing world
Mapping for Accountability: Decolonizing Land Acknowledgment Initiatives
Get PDFWhat does it mean to map Indigenous presence onto lands that have been appropriated by settler colonial nation states? This chapter examines the challenges and potentials of re-inscribing Indigenous land relations through a digital mapping project, Indigenous Pennsylvania: Past, Present and Future. Situating itself within the growing scholarship of Indigenous cartographies, the chapter presents Indigenous Pennsylvania as an example of d-ecomedia, a shorthand we offer for ecomedia projects that foreground decolonial methodologies. Such methodologies prompt us to attend to a storied sense of Indigenous place-based relations through attention to Indigenous spatial and temporal modes of mediation
Winston Churchill in Manhattan, March 25, 1949
No full textChurchill made his sixth peacetime visit to the United States in March 1949. It was meant in part to be an opportunity for relaxing and sightseeing with his wife, Clementine, and daughter Mary. The Churchill party was rounded out by Mary’s husband Christopher Soames, two secretaries, a detective, and a valet. Churchill’s finances were, according to his leading biographer, Martin Gilbert finally “in order,” and he was able to devote attention to the Cold War and the prospects of peace. [excerpt
Driven to Succeed, or to Leave? The Variable Impact of Self-Leadership in Rideshare Gig Work
No full textThe nature of gig work – temporary, task-based work that is facilitated by applications and platforms – lacks the structural, interpersonal, and organizational dynamics of leadership. Instead, algorithms and software are the primary source of organizational and informational resources for a gig worker in a process known as ‘algorithmic management’. Job performance and career success depends primarily on the individual gig worker’s ability to establish objectives, identify strategies, and develop skills for job performance on their own. As such, success in gig work is likely to be connected to self-leadership ability. Drawing on the psychological perspectives of control theory and conservation of resources theory, we find that the agency provided by self-leadership is generally beneficial to rideshare drivers (N = 924) in that it increases both well-being and the intention to seek non-gig work. However, enacting this agency as a leaderless worker is an intensive process, and can either be a resource gain or drain. We find that workers experience better or worse outcomes, respectively, under circumstances of high job satisfaction or high financial stress. Implications and directions for future HRM research and practice among other gig and traditional worker populations are discussed
Mixed-Species Assemblages and Disease: the Importance of Differential Vector and Parasite Attraction in Transmission Dynamics
No full textIndividuals from multiple species often aggregate at resources, group to facilitate defense and foraging, or are brought together by human activity. While it is well-documented that host-seeking disease vectors and parasites show biases in their responses to cues from different hosts, the influence of mixed-species assemblages on disease dynamics has received limited attention. Here, we synthesize relevant research in host-specific vector and parasite bias. To better understand how vector and parasite biases influence infection, we provide a conceptual framework describing cue-oriented vector and parasite host-seeking behaviour as a two-stage process that encompasses attraction of these enemies to the assemblage and their choice of hosts once at the assemblage. We illustrate this framework, developing a case study of mixed-species frog assemblages, where frog-biting midges transmit trypanosomes. Finally, we present a mathematical model that investigates how host species composition and asymmetries in vector attraction modulate transmission dynamics in mixed-species assemblages. We argue that differential attraction of vectors by hosts can have important consequences for disease transmission within mixed-species assemblages, with implications for wildlife conservation and zoonotic disease
Ventanas Abiertas II
No full textThis book is the second in our introductory sequence of the Spanish language. We designed it to accompany our Spanish 102 course at Gettysburg College. In it you will find sections on vocabulary, grammar, and culture, all with helpful links and videos to enhance student learning. Each chapter provides an introductory statement on its specific learning objectives as well as links to the individual lessons. In turn, at the end of each lesson there are communicative activities to work on in the classroom.https://cupola.gettysburg.edu/oer/1014/thumbnail.jp
APPC Minutes - March 14, 2023
No full textMinutes of the Academic Policy and Program Committee Meeting, March 14, 202
The Troubles on the Brink of Recurrence: Northern Ireland in a Post-Brexit World
Get PDFThe Troubles were a difficult and trying time for Northern Ireland beginning in the 1960s. The subsequent decades were filled with turmoil and violence, mainly centered in Belfast amongst the Protestant and Catholic groups. In 1998, peaceful means to ending the Troubles were accomplished through the Good Friday Agreement. The accord established peace primarily through implementing a new power sharing government, ending direct rule by the British, disarming the paramilitary groups and creating a soft border between Ireland and Northern Ireland. The European Union was a critical asset in negotiating terms for peace. The aid of the European Union helped unite the governments in Dublin, Belfast, and London through not only a common set of policies and political space but through the mutual identity of Europeans. The co-cooperation all came to a crashing halt when the United Kingdom voted to leave the EU in 2016 without regard for Northern Ireland. Brexit poses a major threat to the maintenance of peace in Northern Ireland and goes against the principles laid out in the Good Friday Agreement. Long-term instability has persisted in Northern Ireland ever since, resulting in a renewal of sectarian violence on the one hand and calls for Irish unity on the other. However, it ultimately remains unclear what the outcome will be in this precarious situation. This paper addresses the complexities associated with Brexit in Northern Ireland and long term effects politically, religiously, and economically