#### Fitness

Species interactions (i.e., neighbor treatment) and habitat had significant effects on total fitness for both *M. guttatus* and *M. laciniatus* (Fig. 2, Table 2). However, species interactions primarily affected survival, whereas habitat had significant effects on both survival and fecundity (Figs. 3, 4, Table 2).

Survival in *M. guttatus* was highly dependent on habitat (*F*_{2,304.2} = 8.56, *P* = 0.0002). *M. guttatus* individuals in the seep were 3.58 times less likely to survive to reproduction than individuals in the meadow habitat, and 2.98 times less likely than individuals in the stream habitat [Fig. 3; 95% CI for odds ratios: seep/meadow (1.84, 6.99), seep/stream (1.59, 5.59)]. There was no significant difference in survival between the meadow and stream habitats for either species (*M. guttatus: t*_{167.9} = 1.44, *P* = 0.7012; *M. laciniatus*:* t*_{213.2} = −0.29, *P* = 0.9997). The probability of survival for *M. laciniatus* did not differ among habitats (*F*_{2,183.8}=1.05, *P* = 0.3524). Fecundity followed the same general pattern, with strong habitat effects for *M. guttatus,* but not *M. laciniatus* (Fig. 4; *M*. *guttatus*:* F*_{2,127} = 6.57, *P* = 0.0019; *M*. *laciniatus*:* F*_{2,75.5} = 0.99, *P* = .3782). *M. guttatus* individuals produced significantly more seed in the meadow than in the stream habitat (*t*_{83.3} = 3.48, *P* = 0.0078).

Overall, interspecific interactions were competitive (total fitness: *t*_{507.5} = 3.28, *P* = 0.0011; survival: *t*_{562} = 2.99, *P* = 0.0029; fecundity: *t*_{221.5} = 0.26, *P* = 0.7930), whereas intraspecific interactions were marginally facilitative (total fitness: *t*_{508} =1.88, *P* = 0.0607; survival: *t*_{562} =1.91, *P* = 0.0572; fecundity: *t*_{228.3} =0.23, *P* = 0.8208) (Fig. 2-4). The effect of species interactions differed among habitats (Table 2). Interspecific competition was more intense in the meadow habitat relative to the stream habitat for fecundity (*t*_{216.1} =2.08, *P* = 0.0388), and marginally so for survival (*t*_{562} =1.68, *P* = 0.0936) and total fitness (*t*_{507.9} =1.71, *P* = 0.0872) (Fig. 2-4). However, the intensity of intraspecific interactions did not differ statistically among habitats for any fitness components (Tables S1–S3). There was no evidence that *M. guttatus* and *M. laciniatus* differed in the intensity of either interspecific (total fitness: *t*_{509.2} = −0.43, *P* = 0.6659; survival: *t*_{562} = 1.41, *P* = 0.1587; fecundity: *t*_{215.2} = −1.58, *P* = 0.1149) or intraspecific interactions (total fitness: *t*_{509.7} = −0.10, *P* = 0.9176; survival: *t*_{562} = 1.18, *P* = .2397; fecundity: *t*_{215.2} = −1.17, *P* = 0.2438).

In the seep, there were strong differences in survival between *M. guttatus* and *M. laciniatus* (*F*_{1, 144} = 19.54, *P* < 0.0001). *M. laciniatus* was 10.53 times more likely to survive to reproduction than *M. guttatus* (95% CI for odds ratio: 3.68, 30.30). Interspecific competition was strong as individuals grown alone were 5.47 times more likely to survive to reproduction than those in interspecific treatments (95% CI for odds ratio: 1.04, 28.81); there was no significant difference between alone and intraspecific treatments. The strength of interspecific competition did not differ between *M. guttatus* and *M. laciniatus* (*F*_{2,144} = 0.42, *P* = 0.6574). There were no significant effects of species identity (*F*_{1,28.2} = 1.12, *P* = 0.2993) or neighbor treatment (*F*_{2,27.1} = 0.34, *P* = 0.7149) on fecundity.

In the meadow habitat, the relative performance of either species was dependent on the dominant neighboring species. *M. * *laciniatus* with intraspecific neighbors outperformed *M. guttatus* with interspecific neighbors in both total fitness and survival (total fitness: *t*_{157} = 3.79, *P* = 0.0029; survival: *t*_{174} = 4.3, *P* = 0.0004) (Figs. 2-4). Similarly, *M. guttatus* with intraspecific neighbors outperformed *M. laciniatus* with interspecific neighbors in total fitness (*t*_{157} = 4.14, *P* = 0.0008), with a marginally significant difference in survival (*t*_{174} = 2.61, *P* = 0.10). There were no species differences in either total fitness (*t*_{158} = .57, *P* = 0.5712) or survival (*t*_{174} = 1.18, *P* = 0.2398), although *M. guttatus* did exhibit marginally greater fecundity (*t*_{79.6} = 1.84, *P* = 0.0696). Rather, species interactions had strong effects on total fitness (*F*_{2,157} = 15.95, *P* < 0.0001) and survival (*F*_{2,16.92} = 12.96, *P* = 0.0004). Individuals in intraspecific treatments were 3.86 times more likely to survive to reproduction than individuals grown alone, and 8.47 times more than individuals grown with interspecific competitors [95% CI for odds ratios: intraspecific/alone (1.06, 13.89), intraspecific/interspecific (3.58, 20)]. There was no evidence that the strength of these interactions differed between species for either total fitness (*F*_{2,158} = 0.30, *P* = 0.7412) or survival (*F*_{2,174} = 0.94, *P* = 0.3921).

In the stream habitat, *M. laciniatus* outperformed *M. guttatus* in total fitness (*F*_{1, 220} = 14.25, *P* = 0.0002), survival (*F*_{1,244} = 14.03, *P* = 0.0002), and fecundity (*F*_{1,102} = 5.46, *P* = 0.0214). *M. laciniatus* was 2.9 times more likely to survive to reproduction than *M. guttatus* (95% CI for odds ratio: 1.66, 5.08), and had greater first year fecundity (*t*_{102} = 2.34, *P* = 0.0214). However, the subset of *M. guttatus* individuals left to overwinter in this habitat grew larger in the second year than *M. laciniatus* grows in any of the local habitats (J. Sexton, *unpubl. data*). Additionally, species interactions affected the probability of survival (*F*_{2,244}=3.29, *P* = 0.0388), but not fecundity (*F*_{2,104}=.73, *P* = 0.4843). Individuals in intraspecific treatments were 2.2 times more likely to survive to reproduction than individuals in interspecific treatments (95% CI for odds ratio: 1.19, 4.07). The strength of this effect did not differ between species (*F*_{2,244} =** **0.07, *P* = 0.9354).

##### Phenology

There were significant differences in flowering time among species, with *M. laciniatus* having a higher probability of flowering in all three habitats (Fig. 5; Seep: χ^{2} = 25.354, *P* < 0.0001; Meadow: χ^{2} = 17.353, *P* < 0.0001; Stream: χ^{2} = 30.831, *P* < 0.0001). Neighbor effects on flowering were significant in all three habitats; the presence of either inter- or intraspecific neighbors increased the probability of flowering relative to treatments without neighbors (Fig. 5; Seep: χ^{2} = 13.087, *P* = 0.0014; Meadow: χ^{2} = 17.998, *P* = 0.0001; Stream: χ^{2} = 20.933, *P* < 0.0001). In the meadow habitat, there was a significant species-by-neighbor treatment interaction, with *M. laciniatus* flowering earlier in response to neighbors than *M. guttatus* (χ^{2} = 10.85, *P* = 0.0044).