Brenda Molano-Flores

THE EFFECT OF POPULATION SIZE ON STIGMA POLLEN LOAD, FRUIT SET, AND SEED SET IN ALLIUM STELLATUM KER. (LILIACEAE)

In Allium stellatum, a xenogamous self‐compatible prairie species, we examined stigma pollen load, percentage of fruit set, and percentage of seed set in large and small populations over 2 yr. We tested for significant effects of population size on these characteristics, for relationships between stigma pollen loads and fruit and seed set, and for significant variation between years in reproductive characteristics. In 1994 stigma pollen loads were inversely related to population size and were significantly lower than in 1993. The lower stigma pollen loads in 1994 were associated with adverse weather conditions (high rainfall), which are known to affect pollinator activity and may have led to competition among plants for pollinators in large populations. However, population size was not correlated with percentage of fruit set or percentage of seed set in either year. The lack of fruit and seed set differences between large and small populations, particularly in 1994, likely resulted from the small amount of pollen needed to trigger fruit and seed production. Our results indicate that for some self‐compatible species that similarly require small pollen loads, the effects of population size on reproduction are minimal, even if differences in pollen‐movement exist between large and small populations.

The Effects of Population Size and Density on the Reproductive Output of Anemone canadensis L. (Ranunculaceae)

We studied the effects of population density and population size on stigma pollen load and fruit set in Anemone canadensis, a xenogamous self‐incompatible species. In 1993, 1994, and 1995, we examined 13–17 populations, with densities ranging from one to 39 flowering ramets per square meter and sizes ranging from 25 to 27,000 flowering ramets. In 1993, stigmas received fewer pollen grains than in 1994 or 1995. In 1993 and 1995, population size and fruit set were significantly and positively related, and in 1993, both population density and stigma pollen load were significantly and positively related to fruit set. Stigma pollen load was not significantly related to population density or size. Our results indicate that the effects of population density and population size on plant reproduction in A. canadensis represent a range of outcomes influenced by differences between years in the quality (self vs. outcross) of pollen moved. We hypothesize that small populations typically have poor fruit set because they consist of relatively few genets and infrequently receive large amounts of outcross pollen, particularly when they are relatively close to large populations in protected areas.

Effects of herbivory and inflorescence size on insect visitation to eryngium yuccifolium (Apiaceae) a prairie plant

Abstract Herbivory and inflorescence size can influence floral visitors. Damaged inflorescences have been shown to have fewer floral visitors due to changes in floral appearance/chemistry, whereas larger inflorescences attract more pollinators because of greater pollen/nectar reward. This study examined whether floral herbivory by a moth, Coleotechnites eryngiella Bottimer (Gelechiidae), and inflorescence size have any effect on the attractiveness of Eryngium yuccifolium Michaux (Apiaceae) to floral visitors. In particular, the study seeks to determine how combined effects of inflorescence size and herbivory affect overall and main composition of floral visitors groups. Twelve plants, six with one inflorescence stalk (three with and three without herbivory) and six with three inflorescence stalks (three with and three without herbivory) were observed for floral visitors in 2004 and 2007 at four remnant tallgrass prairies located in east-central Illinois, USA. Damaged inflorescences had lower flower visitation than undamaged inflorescences. Larger floral displays attracted more floral visitors. Differences between the numbers of flies, bees and beetles visiting the flowers were not independent of herbivory and inflorescence size. This study provides additional evidence that herbivory and inflorescence size can influence insect visitation. In addition, this study provides further support to recent publications regarding the more sophisticated nature of the pollinator guild associated with members of Apiaceae. Finally, it also provides the foundation for future studies to determine how differences in the composition of floral visitors are associated with the male and female inflorescence phases of E. yuccifolium and their relation to male and female fitness.

Pollination biology and flower visitors of the gynodioecious species Lobelia spicata Lam. (Campanulaceae)

Molano-Flores, B. (Illinois Natural History Survey-Center for Biodiversity, 607 E. Peabody Drive, Champaign, Illinois 61820). Pollination biology and flower visitors of the gynodioecious species Lobelia spicata Lam. (Campanulaceae). J. Torrey Bot. Soc. 129: 187-193. 2002.-The pollination biology and flower visitors of Lobelia spicata, an herbaceous prairie perennial, were examined, and this species was found to be xenogamous, self-compatible, and gynodioecious. Hermaphroditic individuals are protandrous, produce nectar, and have secondary pollen presentation (i.e., pump mechanism). Female individuals do not produce nectar. No significant differences were found between the fruit set of open-pollinated hermaphroditic and female flowers. In hermaphroditic bagged flowers seeds were produced (i.e., undeveloped fruits) suggesting self-pollination; however, this was determined to be the result of geitonogamous pollination by thrips. Autogamy is not likely in this species because there is no overlap between the staminate and pistillate phases. This species is pollinated mainly by bees from the genus Augochlorella. Overall, this study shows that L. spicata shares many common characteristics with other species of Lobelia (i.e., L. cardinalis and L. siphilitica) such as protandry, self-compatibility, no autonomous self-pollination, similar flower phenology (i.e., pistillate and staminate phases), and secondary pollen presentation (i.e., pump mechanism). In contrast to these other species, L. spicata blooms early, has smaller flowers, and attracts smaller pollinators.

The reproductive biology of Agalinis auriculata (Michx.) Raf. (Orobanchaceae), a threatened North American prairie inhabitant

We examined the reproductive biology of the hemiparasitic threatened prairie species, Agalinis auriculata (Michx.) Raf., eared‐false foxglove (Orobanchaceae), in two populations located at the Midewin National Tallgrass Prairie in Illinois. Populations flowered from late August through mid‐September, and individual plants bloomed for an average of 8 d; typically two flowers per plant opened each day. Buds opened in the early morning hours between 0530 and 0630 hours, with the anthers dehiscing at this time. Stigmas reached peak receptivity ca. 2 h later, followed by corolla abscission shortly afterward. Breeding system experiments indicated that flowers readily self‐pollinate without reduction in fruit set, seed set, or seed mass compared with outcrossed individuals. The primary floral visitors were Bombus impatiens (Apidae) and Melissodes bimaculata (Anthophoridae). On the basis of phenological and breeding system data, A. auriculata is a self‐compatible species that self‐pollinates in the absence of floral visitors; however, when pollinators are present, outcrossing can occur. The autogamous nature, in combination with a healthy reproductive output, indicates that the decline of this species might result from other aspects of its biology, such as seed germination and availability of host plants.

Reproductive biology of Eryngium yuccifolium (Apiaceae), a prairie species

MOLANO-FLORES, B. (Illinois Natural History Survey-Center for Biodiversity, 607 E. Peabody Drive, Champaign, IL 61820). Reproductive biology of Eryngium yuccifolium (Apiaceae), a prairie species. J. Torrey Bot. Soc. 128:1-6. 2001. Temporal dioecism is a synchronized flowering sequence with minimal overlap between the pistillate and staminate phases of an individual plant. This strategy allows pollen to be shed before stigmas become receptive, minimizing geitonogamous pollinations and maximizing outcrossing. I studied this condition using Eryngium yuccifolium Michx., a tallgrass prairie perennial species. As a temporaly dioecious species, E. yuccifolium exhibits the following characteristics: 1) an extended pistillate phase, with stigmas becoming receptive only after the anthers have shed pollen and dehisced, 2) synchronized flower heads, 3) numerous flower heads visited by generalist pollinators, and 4) some degree of self-compatibility as indicated by hand pollinations. Finally, results from open and bagged pollinations and high pollen-ovule ratios indicated that the species is xenogamous. This study also found high fruit and seed sets (close to 90%) for E. yuccifolium. However, intense herbivory by the larva of a Gelechiidae moth significantly reduced the reproductive output of the species by destroying 40-60% of flowers and fruits. The results of this study indicate that temporal dioecism can enhance outcrossing and potentially can explain the high fruit and seed set for E. yuccifolium.

Reproductive Success of the Federally Endangered Leafy Prairie Clover, Dalea foliosa (A. Gray) Barneby (Fabaceae) in Illinois: a Third Year of Data

Abstract The federally-endangered species Dalea foliosa (leafy prairie clover) is a short-lived herbaceous perennial found in dolomite prairie. In Illinois, only five populations are known including one at the Midewin National Tallgrass Prairie (MNTP). In this paper, I present the results of a third year of reproductive success data and determine variation between years in reproductive success for this small isolated population. As in 1998 and 1999, 2000 reproductive success was high, although variation between years was found. Although the studied population of D. foliosa is small, isolated, and found in a fragmented habitat, these conditions do not appear to affect reproductive success.

An Invasive Plant Species Decreases Native Plant Reproductive Success

ABSTRACT: Invasive plants may have negative, positive, or neutral effects on the reproductive success of native plant species. In this study, I investigated the impact of the rhizomatous invasive species Securigera varia (Fabaceae; crown vetch; synonym: Coronilla varia) on the reproductive success of the native prairie species Tradescantia ohiensis (Commelinaceae; Ohio spiderwort). In particular, I examined how T. ohiensis plant height, fruit set, seed set, and stigma pollen load differed inside or at the edge of crown vetch patches and within native prairie not invaded by crown vetch. A significant reduction in reproductive success and pollen deposition was detected among T. ohiensis plants in the interior of a crown vetch patch compared to those at the edge of a crown vetch patch. These, in turn, had lower reproductive success and pollen deposition than plants in the native prairie areas. Also, T. ohiensis plants were taller inside crown vetch patches. The results of this study suggest that rhizomatous invasive species such as Securigera varia can have direct and indirect impacts on the reproductive success of native species.

Evaluating hill prairie quality in the Midwestern United States using Auchenorrhyncha (Insecta: Hemiptera) and vascular plants: a case study in implementing grassland conservation planning and management

In this study a habitat quality index based on Auchenorrhyncha (Insecta: Hemiptera) species composition was used to investigate the index’s ability in discriminating hill prairie quality along a gradient of disturbance, based on the Illinois Natural Areas Inventory grading criteria; whether this index differs from other vegetation-based measures of quality; and examine the relationships between Auchenorrhyncha and vegetation integrity and diversity. Auchenorrhyncha and vascular plants were sampled from 14 Illinois glacial-drift hill prairies representing a range in quality. Insects and plants were sampled from late July through August, 2007 and analyzed using univariate and multivariate analyses. Results from this study showed that Floristic Quality Index, Auchenorrhyncha Quality Index, as well as other Auchenorrhyncha and plant diversity and integrity index values are greater in high, followed by mid, then low quality hill prairie remnants. Also, these analyses showed that perennial C4 grasses are strongly associated with prairie Auchenorrhyncha. These data suggest that judicious used of prescribed burning or brush removal may be needed to prevent woody-encroachment from eliminating prairie vegetation and Auchenorrhyncha on low quality sites; and restoration of perennial C4 grasses on low quality sites are needed to support more prairie Auchenorrhyncha fauna. Reintroductions of conservative (i.e., prairie-dependent and fire-sensitive) Auchenorrhyncha may also be needed to improve Auchenorrhyncha integrity on mid and low quality sites but these reintroductions need to be used in combination with reduced burn management or the inclusion of unburned refugia to reduce the extirpation of these fire-sensitive insects.

Germination of Two Seed Types from Three Dalea Species

Abstract Dalea species are legumes that often are included in seed mixtures used for prairie restorations. Three Dalea species (D. foliosa, D. candida, and D. purpurea) exhibit two different types of seeds: plump (well-rounded larger) and dented (wrinkled smaller) seeds. Differences in germination and viability of these two types of seeds have not been reported. Our objectives were to compare seed mass, germination and viability between these types of seeds for three Illinois Dalea species. Fruits were collected for D. foliosa from 1998–2001 (Will County) and for D. candida and D. purpurea from 2001–2003 (Kankakee, Tazewell and Will Counties). For each species, seed mass, germination and viability were determined per seed type (plump or dented). Seed mass was significantly higher for plump than dented seeds for all three species. For D. foliosa and D. candida, germination of dented seed exceeded that of plump seed in some years. For D. purpurea, germination was significantly greater for plump seeds in both years. For ungerminated seeds of D. foliosa, only the plump seeds were viable, whereas for D. candida and D. purpurea, both seed types were viable. A comparison of seed germination among all three species when collected in the same county and year showed lower germination for D. foliosa than for D. candida and D. purpurea. In summary, seed types play a significant role in germination of these three species, and D. foliosa has lower germination than D. candida or D. purpurea.