Tim webpage

RESEARCH INTEREST: My general research interest lie at interface of evolution, ecology and physiology. More generally I am interested in understanding the mechanisms used to integrate and interpret environmental cues to time reproduction. Timing breeding to coincide with favorable environmental conditions increases an animals reproductive success, and are thus extememely important when asking evolutionary and ecological questions. Two recently discovered peptide hormone, kisspeptin and gonadotropin inhibiting hormone (GnIH), appear to play important roles in altering the activity of the reroductive neuroendocrine axis by responding to environmental cues, such as photoperiod and food availability.

DOES KISSPEPTIN REGULATE SEASONAL REPRODUCTION? I am currently investigating the role kisspeptin plays in regulating seasonal patterns in reproduction. We have located kisspeptin neurons in two hypothalamic nuclei, the anterioventral periventricular nucleus (AVPV) and the arcuate nucleus (ARC). In long-summer like days, we found dense staining for kisspeptin in the AVPV; kisspeptin nearly dissapeared in this nucleus in animals held on winter-like short-days. We found the opposite pattern of staining in the ARC; dense staining was found in the ARC in animals held on winter-like short-days, with very little kisspeptin found in animals in summer-like long-days. Additionally, injections of kisspeptin stimulate release of LH in both reproductive and non-reproductive animals. Based on these observations, we have constructed a model of how seasonal breeders may use kisspeptin to integrate relevant environmental cues, such as food availability, temperature and photoperiod.

CONTACT INFORMATION:

Indiana University, Department of Biology
Jordan Hall
1001 East Third St.
Bloomington, IN 47401
tjgreive AT indiana DOT edu

PUBLICATIONS:

2008
Greives, T.J., Humber, S.A., Goldstein, A.N., Scotti, M.A., Demas, G.E., and Kriegsfeld, L.J. In Press. Photoperiod and testosterone interact to drive seasonal changes in kisspeptin expression in Siberian hamsters (Phodopus sungorus). Journal of Neuroendocrinology

Freedberg, S., Greives, T.J., Ewert, M.A., Demas, G.E., Beecher, N., and Nelson, C.E. 2008. Incubation environment affects immune system development in a turtle with environmental sex determination. Journal of Herpetology 42: 536-541.

Greives, T.J., Kriegsfeld, L.J., Bentley, G.E., Tsutsui, K., and Demas, G.E. 2008. Recent advances in reproductive neuroendocrinology: Role for RFamide peptides in seasonal reproduction? Proceedings of the Royal Society of London B 275: 1943-1951. PDF

Greives, T.J., Kriegsfeld, L.J., and Demas, G.E. 2008. Long-term kisspeptin does not alter photoperiod-induced gonadal regression in Siberian hamsters (Phodopus sungorus). General and Comparative Endocrinology 156: 552-558. PDF

Pedersen, A.B., and Greives, T.J. 2008. The interaction of parasites and resources cause crashes in a wild mouse population. Journal of Animal Ecology 77: 370-377. PDF
In Focus Commentary: Ostfeld, R.S. 2008. Parasites as weapons of mouse destruction. Journal of Animal Ecology 77: 201-204. PDF

McGlothlin, J.W., Jawor, J.M., Greives, T.J., Casto, J.M., Phillips, J.L., and Ketterson, E.D. 2008. Hormones and honest signals: males with larger ornaments elevate testosterone more when challenged. Journal of Evolutionary Biology 21: 39-48. PDF

2007
Mason, A.O., Greives, T.J., Scotti, M.A., Ketterson, E.D., Demas, G.E., and Kriegsfeld, L.J. 2007. Suppression of kisspeptin expression and gonadotropic axis sensitivity following exposure to inhibitory day lenghts in female Siberian hamsters. Hormones and Behavior 52: 492-498. PDF

Jawor, J.M., McGlothlin, J.W., Casto, J.M. Greives, T.J., Snajdr, E.A., Bentley, G.E., and Ketterson, E.D. 2007. Testosterone response to GnRH in a female songbird varies with stage and reproduction: implications for adult behaviour and maternal effects. 2007. Functional Ecology 21: 767-775 PDF

Greives, T.J., Casto, J.M and Ketterson, E.D. 2007. Relative abundance of males to females affects behaviour, condition and immune function in a cpative population of dark-eyed juncos Junco hyemalis. Jorunal of Avian Biology 38:255-260. PDF

Greives, T.J., Mason, A.O., Scotti, M.L., Ketterson, E.D., Kriegsfeld, L.J. and Demas G.E. 2007. Environmental control of kisspeptin: Implications for seasonal reproduction. Endocrinology 148: 1158-1166. PDF

2006
Greives, T.J., McGlothlin, J.W., Jawor, J.M., Demas, G.E., and Ketterson, E.D. 2006 Testosterone and innate immune function inversely co-vary in a wild population of breeding Dark-eyed Juncos (Junco hyemalis). Functional Ecology 20: 812-818. PDF

Jawor, J.M., McGlothlin, J.W., Casto, J.C., Greives, T.J., Snajdr, E.A., Bentley, G.E., and Ketterson, E.D. 2006. Seasonal and individual variation in response to GnRH challenge in male dark-eyed juncos (Junco Hyemalis). General and Comparative Endocrinology 149: 182-189. PDF

Zysling, D.A., Greives, T.J., Breuner, C., Casto, J.M., Demas, G.E., and Ketterson, E.D. 2006. Behavioral and physiological responses to experimentally elevated testosterone in female Dark-eyed Juncos (Junco hyemalis carolinensis). Hormones and Behavior 50: 200-207. PDF