Alternative reproductive tactics, an overlooked source of life history variation in the invasive round goby

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 76; no. 9; pp. 1562 - 1570
• Main Authors: McCallum, Erin S, Bose, Aneesh P.H, Lobban, Naylor, Marentette, Julie R, Pettitt-Wade, Harri, Koops, Marten A, Fisk, Aaron T, Balshine, Sigal
• Format: Journal Article
• Language: English
• Published: Ottawa NRC Research Press 01.09.2019; Canadian Science Publishing NRC Research Press
• Subjects: Analysis; Animal reproduction; Athletic shoes; Breeding; Diet; Fish; Fishes; Freshwater; Inland waters; Introduced species; Invasive fish; Invasive species; Isotopes; Lakes; Life history; Males; Marine fishes; Neogobius melanostomus; Niches; Populations; Questions; Reproduction; Studies; Tactics; Trophic levels; Variation; Canada; USA, Michigan, Laurentian Great Lakes
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/cjfas-2018-0340

Alternative reproductive tactics (ARTs) can generate considerable within-species life history variation but are often overlooked. Here, we use the invasive round goby (Neogobius melanostomus) to address a number of ecological and evolutionary questions about ARTs. Making use of a 12-year, multisite Laurentian Great Lakes data set, we show that the guarder male tactic was twice as common as the sneaker male tactic but that nonreproductive males were the most common morph. The ratio of guarder to sneaker males did not vary spatially despite a wide range of resource densities across sites. Guarders and sneakers spanned similar age ranges, suggesting that the ARTs are nonsequentially expressed. Based on short-term (gut contents) diet analyses, both reproductive tactics consumed fewer types of food and tended to consume fewer items overall when compared with nonreproductive males. Long-term (isotope) diet analyses showed that guarder males fed at a higher trophic level (higher δ 15 N) and had a broader isotopic niche. Our results show that ARTs are an important aspect of this invasive species’ breeding system and should be accounted for when assessing and managing populations.