ABSTRACT Ecological life periods g...

ABSTRACT

Ecological life periods growth characteristics, and flowering requirements of the sum of two units closely-related species Penstemon tenuiflorus and P hirsutus were compared via a combination of field, greenhouse, and growing chamber studies. In addition, field observations were made upon plant-animal interactions involving these sum of two units species. Both species are hemicryptophytes that copy by seeds and by vegetative offsets and their life cycle stages, phenology (where their ranges overlap in northcentral Tennessee) germination characteristics, and flowering requirements are the same. Plants flower in spring, and originals are mature by late summer; se dispersal lasts from late summer until early spring. originals germinate primarily in early spring, and plants form a rosette their first year; neither species forms a persistent se bank. In a nonheated greenhouse, plants darted and flowered in their other year, whereas in the field bolting and flowering are delayed until at least the fourth year. Neither without deductions assimilation rate, relative growth rate, nor eight of 10 other parameters of shooting differed between plants of the sum of two units species grown under greenhouse conditions. Plants of the two species require exposure to several hundr hours of vernalizing temperatures to flower; however, they are indifferent to photoperiod with regard to flowering (i.e., day-neutral). Leaves of P tenuiflorus are brows through cottontail rabbits and inflorescences by way of whitetail deer, and seeds of the two species are predated by lepidopteran larvae. Thus, the ecological life period growth characteristics, physiological requirements for evolution and plant-animal interactions are true similar in these two taxonomically-distinct species. It pretends unlikely that any of these aspects of their autecology accounts for differences between them either in geographical distribution or habitat ecology

INTRODUCTION

An objective of the discipline of ecology is to understand the complexity and diversity in morphology, physiology, life history, and other attributes of plants that determine their ecology (Clapham 1956 Grime 1984) To attain this goal, comparison, which is a mode of study, has to be used (Bradshaw 1987) Bradshaw (1987) stated that, " . we can have no idea about the significance of a particular species' distribution unles we have single for a second with which to compare it." We have used the comparative approach to investigate the ecology of Penstemon tenuiflorus Pennell and P hirsutus (L) Willd. (Scrophulariaceae), sum of two units taxonomically closely-- related, interfertile members of Section Graciles in eastern North America (Pennell 1935 Koelling 1964 Crosswhite 1965 milds et al. 1998). Although there have been quite a scarcely any reports on some aspects of the life revolution of time biology of Penstemon species (eg se germination, diocese RESULTS AND DISCUSSION), our reflection on P tenuiflorus and P hirsutus is the first to include all major stages of the life circle of time It also is the first comprehensive close attention on the comparative biology of Penstemon species, rare or otherwise.

The geographic range of Penstemon tenuiflorus widens from western Kentucky to the Black Belt of Alabama and Mississippi and that of P hirsutus from western Virginia and northcentral Tennessee to Wisconsin, Ontario, Quebec, and Maine (Clement et al. 1998) Penstemon tenuiflorus lately was reported, apparently for the first time, from the Ridge and Valley Physiographic Province, growing forward the Ketona dolomite outcrops in Bibb shire Alabama (Allison and Stevens 2001) Penstemon tenuiflorus put forths in open rocky woods, cedar glades, chalk prairies, xeric limestone prairies (prairie barrens), and (rarely) onward river cliffs, usually on calcareous substrate (Clement 1995 Morris et al. 1993 Webb et al. 1997 Allison and Steven 2001) The habitat of P hirsutus includes free from moisture sandy or rocky open timber-lands rocky bluffs, rocky shores of lakes, alvars, hard barrens, gravel hill prairies, and sand prairies (Gleason 1910 Core 1948 employment et al. 1985, Bartgis 1993 compassionates 1995, Catling and Brownell 1999) Within their geographic range of overlap in northcentral Tennessee and southcentral Kentucky the brace taxa occupy different habitats, primarily limestone cedar glades for P tenuiflorus and limestone cliffs for P hirsutus.

This is the third in a series of papers forward the comparative biology of Penstemon tenuiflorus and P hirsutus. In the first paper, indulgents et al. (1998) demonstrated that differences in leaf pubescence and flower color, at which these two taxa easily are distinguished in the field, were maintained in a less degree than uniform growth conditions for 4 years (until investigation ended). On the other hand, an SEM close attention showed that they did not differ in se coat or pollen morphology (Clement et al. 1998) In the inferior paper, Clements et al. (1999) showed that flowering pattern for flowers and for inflorescences, flowering phenology, and mating scheme of these two species are the same. Further, breed resulting from selfing in P tenuiflorus did not exhibit inbreeding depression as measured on seed weight, seed germination, and various development parameters (P hirsutus progeny not proofed for inbreeding depression). However, in as well-as; not only-but also; not only-but; not alone-but P tenuiflorus and P hirsutus significantly fewer first principles were produced by outcrossed than on selfed flowers. As a further contribution to the comparative biology of P tenuiflorus and P hirsutus, the ready study investigated their ecological life revolution of times growth characteristics, and physiological requirements for flowering. In addition, plants of the sum of two units species were observed in the field for disease, herbivory, and se predation.