Germination of One-Seed Juniper Seeds Distributed by Different Frugivore Groups

Abstract

One-seed juniper (Juniperus monosperma [Englem.] Sarg.) encroachment into grassland habitats is facilitated by a diverse group of frugivores. To test seed germination after gut passage, we collected pellets or scats containing mature seeds from four frugivore groups: passerine (perching) birds, lagomorphs (hares and rabbits), mesocarnivores (coyotes and foxes), and porcupines. For comparison of germination success, we also evaluated seeds from intact, nondigested one-seed juniper cones. We conducted germination trials under three different scenarios: 1) imbibed bare seeds (a measure of potential germination); 2) seeds still encased within a frugivore deposited pellet or scat matrix or still in a nondigested cone; and 3) matrix-free seeds that had gone through the matrix germination trials and then were freed from the matrix (a simulation of seeds that become dislodged from scats or pellets). In the bare seed trials, germination was highest (70.8% ± 7.4%) for seeds digested by mesocarnivores and was 63.9% ± 5.7% for porcupines, which was higher (P < 0.05) than germination of seeds from bird pellets (33.3% ± 7.7%). Germination of seeds from all frugivores, including lagomorphs (51.4% ± 7.2%), was higher (P < 0.05) than for seeds encased in cones (9.7% ± 3.2%). The germination percentage of seeds still encased in frugivore pellets or scats was highest for birds (40.1 ± 4.2) and was significantly lower (P < 0.05) for other frugivores. Seeds freed from all frugivore deposition matrices showed a second pulse of germination activity, especially seeds from lagomorph pellets. Germination success differences can influence the nature of one-seed juniper woodland infill and encroachment into bordering grasslands, which can lead to loss of soil health, lower grass biomass production, and a diminishment of habitat quality for grassland-dependent wildlife species.