Question

1. Thinking about life histories,
   1. Describe the life histories of clover. You may have to do some additional research for this. (6 pts)
2. For each, is it semelparous or iteroparous? Explain. (6 pts)
3. For each, is it r-selected or K-selected? Explain. (6 pts)

Answer 1

a) Clover or trefoil are common names for plants of the genus Trifolium (Latin, tres "three" + folium "leaf"), consisting of about 300 species of flowering plants in the legume or pea family Fabaceae. The genus has a cosmopolitan distribution with the highest diversity in the temperate Northern Hemisphere, but many species also occur in South America and Africa, including at high altitudes on mountains in the tropics. They are small annual, biennial, or short-lived perennial herbaceous plants. Clover can be evergreen. The leaves are trifoliate (rarely quatrefoils; see four-leaf clover), cinquefoil, or septfoil, with stipules adnate to the leaf-stalk, and heads or dense spikes of small red, purple, white, or yellow flowers; the small, few-seeded pods are enclosed in the calyx. Other closely related genera often called clovers to include Melilotus (sweet clover) and Medicago (alfalfa or Calvary clover).

The most important agricultural species are red clover (Trifolium pratense), white clover (T. repens), and alsike clover (T. hybridum). Red clover, a biennial, or short-lived perennial, bears an oval purplish flower head about 2.5 cm (1 inch) in diameter. White clover, a low creeping perennial, is often used in lawn-grass mixtures and bears a white flower head often tinged with pink. Alsike clover, a perennial species sometimes called Swedish clover, or Alsatian clover bears globular rosy-pink flower heads. Clovers are generally short-lived herbs and feature alternate compound leaves, usually with three toothed leaflets. The very small, fragrant flowers are crowded into dense, nearly spherical heads, or spikes and can be white, pink, red, or yellow. The small, dry fruits usually contain one or two seeds. Many species tolerate shade, repeated mowing, and foot traffic very well and are often found in lawns. The plants are susceptible to alfalfa weevils and a number of foliar diseases, including common leaf rot and mosaic.

b) Semelparity and iteroparity are two classes of possible reproductive strategies available to living organisms. A species is considered semelparous if it is characterized by a single reproductive episode before death and iteroparous if it is characterized by multiple reproductive cycles over the course of its lifetime.

In truly semelparous species, death after reproduction is part of an overall strategy that includes putting all available resources into maximizing reproduction, at the expense of future life (see "Trade-offs", below). In any iteroparous population, there will be some individuals who die between their first and second reproductive episodes, but unless this is part of a syndrome of programmed death after reproduction, this would not be called semelparity.

This distinction is also related to the difference between annual and perennial plants. An annual is a plant that completes its life cycle in a single season and is usually semelparous. Perennials live for more than one season and are usually (but not always) iteroparous.

Semelparity and iteroparity are not, strictly speaking, alternative strategies, but extremes along a continuum of possible modes of reproduction. Many organisms considered to be semelparous can, under certain conditions, separate their single bout of reproduction into two or more episodes.

c)The two evolutionary "strategies" are termed r-selection, for those species that produce many "cheap" offspring and live in unstable environments and K-selection for those species that produce few "expensive" offspring and live in stable environments.

r-selection: On one extreme are the species that are highly r-selected. r is for reproduction. Such a species puts only a small investment of resources into each offspring, but produces many such low effort babies. Such species are also generally not very invested in protecting or rearing these young. Often, the eggs are fertilized and then dispersed. The benefit of this strategy is that if resources are limited or unpredictable, you can still produce some young. However, each of these young has a high probability of mortality, and does not benefit from the protection or nurturing of a caring parent or parents. r-selected babies grow rapidly, and tend to be found in less competitive, low quality environments. Although not always the case, r-selection is more common among smaller animals with shorter lifespans and, frequently, non-overlapping generations, such as fish or insects. The young tend to be precocial (rapidly maturing) and develop early independence.

K-selection: On the other extreme are species that are highly K-selected. K refers to the carrying capacity, and means that the babies are entering a competitive world, in a population at or near its carrying capacity. K-selected reproductive strategies tend towards heavy investment in each offspring, are more common in long-lived organisms, with a longer period of maturation to adulthood, heavy parental care and nurturing, often a period of teaching the young, and with fierce protection of the babies by the parents. K-selected species produce offspring that each have a higher probability of survival to maturity. Although not always the case, K-selection is more common in larger animals, like whales or elephants, with longer lifespans and overlapping generations. The young tend to be altricial (immature, requiring extensive care).