Variation in Reproductive Traits of Female Fourspine Stickleback (Apeltes quadracus) in Nova Scotia, Canada

The Fourspine Stickleback (Apeltes quadracus) is a diminutive member of the Gasterosteidae inhabiting a rather narrow zone comprising coastal and near-coastal brackish and freshwater habitats from the Gulf of St. Lawrence to North Carolina. Behavior, morphology, and several other aspects of the biology of A. quadracus have been well studied, yet there are surprisingly few investigations of its life history. Here, we provide data on four reproductive traits for female A. quadracus from seven sites in Nova Scotia, Canada. The sites occur within three distinct regions of Nova Scotia, and encompass a variety of brackish-water and freshwater habitats. Female size, clutch mass adjusted to a common body size, and clutch size adjusted to a common body size differed significantly among the three regions. These traits also showed significant variation across sites within regions. Egg dry mass did not differ across regions, but there was significant variation across sites within regions. Our study, and earlier ones from more southern populations, indicate that there may be variation of evolutionary interest in several traits on multiple spatial scales in this species.

Figure 1

Nova Scotia, Canada, showing the approximate location of the seven sampling sites within the three study regions.

Figure 2

The distribution of somatic mass of female Apeltes quadracus within three sampling regions of Nova Scotia, Canada, and pooled across all regions.

Figure 3

The relationship between clutch mass and female somatic mass in female Apeltes quadracus from three regions of Nova Scotia. Note that clutch mass (CM) is dry, while female somatic mass (SM) is blotted wet. Log-log regression equations are: Cape Breton Island [open squares, solid line]: logCM = 0.825*logSM−1.824; Bay of Fundy [closed circles, dashed line]: logCM = 0.807*logSM−1.661; Antigonish [open triangles, dotted line]: logCM = 0.641*logSM−1.926.

Figure 4

Clutch masses of female Apeltes quadracus from seven sites in Nova Scotia. Values are least squares means from ANCOVA adjusted to the overall mean log female somatic mass (females with fully developed eggs only) of −0.262 g. Bars indicate simultaneous 95% confidence limits. Symbols indicate separate populations within each region, with numbers indicating specific populations identified in Table 1.

Figure 5

Clutch sizes of female Apeltes quadracus from seven sites in Nova Scotia. Values are least squares means from ANCOVA adjusted to the overall mean log female somatic mass of −0.238 g (all females that were producing a clutch, whether or not the eggs were fully developed). Bars indicate simultaneous 95% confidence limits. Symbols indicate separate populations within each region, with numbers indicating specific populations identified in Table 1.

Figure 6

Mean dry egg masses of female Apeltes quadracus from seven sites in Nova Scotia. Bars indicate simultaneous 95% confidence limits. Symbols indicate separate populations within each region, with numbers indicating specific populations identified in Table 1.

Contributor Notes

¹ Department of Biology, Lasry Center for BioScience, Clark University, 950 Main Street, Worcester, Massachusetts 01610, e-mail: (JAB) jbaker@clarku.edu. Send reprint requests to JAB.

Associate Editor: S. E. Wise.

Received: 14 Oct 2007

Accepted: 16 Feb 2010