Rough agalinis (Agalinis aspera) COSEWIC assessment and status report: chapter 6
Biology
All information on the biology of this species is contained within studies of the genus as a whole, especially Pennell’s 1929 and 1935 monographs. No publications have been found that are written specifically about this species.
Life cycle and reproduction
This is an annual species that blooms from late July / early August until the end of August / early September and produces seeds in September. The flowers are perfect, occurring in indeterminate racemes in the axils of opposite bracts.
The large flower corolla is attractive to pollinating insects such as bumblebees (Pennell 1935). The spreading lobes of the corolla are specifically adapted to pollination by bees as are the stamens, which have short filaments thereby positioning the anthers within the corolla. In a study of Agalinis acuta (Neel 2002), it and other species of Agalinis were found to be self-compatible. Thus even a very isolated plant may still be capable of producing seed. Although this feature has not yet been studied in A. aspera, the placement of anthers and stigma within the flower make it possible that it could be autogamous (self-fertilized; Canne-Hilliker, pers. comm. 2004). This is a significant feature considering the small size of the Manitoba populations.
The leaf blades are narrow and structurally reduced. This may represent an adaptation to the dry prairie environment, i.e., a xerophytic modification.
Herbivory/predation
No information available under this subheading.
Physiology
No information available under this subheading.
Dispersal/migration
The 1.2 to 1.4 mm seeds are oval-angulate, somewhat diamond shaped (Pennell 1929). Numerous small light seeds are produced per capsule (Figure 4). They probably disperse locally by being blown in the wind when the mature capsules open, although some may be picked up on the feet of birds (Pennell 1935) and other animals.
Interspecific interactions
Agalinis is a hemiparasitic genus. The roots of the Agalinis connect to the host xylem via specialized roots called haustoria, by which they are able to obtain water and dissolved nutrients. The size and vigour of the hemiparasite depends on the availability of host roots and the host type (Musselman and Mann 1978).
Agalinis tenuifolia has been recorded to parasitize a variety of Angiosperm hosts including: Paspalum pubescens, Panicum dichotomum, Agrostis perennans, Juncoides campestre, Anemone virginiana, Rubus villosus, Fragaria virginiana, Potentilla pumila, Viola triloba, Mitchella repens, Solidago bicolor, S. caesia, S. nemoralis, Aster undulatus, Antennaria plantaganifolia and Achillea millefolium (Pennel 1929). Musselman and Mann (1978) found Agalinis to have “the broadest host range of any root parasite in the South”. Although they found no definite host preference by any species of Agalinis, they did note that Agalinis purpurea is never abundant in areas without woody plants. Host preference in A. aspera is not currently known, but one of the most vigorous plants observed in this study was close to a small snowberry bush (Symphoricarpos albus). The two field populations were not far from clumps of aspen (Populus tremuloides).
Adaptability
No information available under this subheading.