Speciation usually relies on the isolation (either geographical or reproductive) of a group of individuals. The coconut example would be unlikely to lead to speciation due to the fact that that it is only one coconut. If many coconuts arrived, then it would be much more likely.

Allopatric speciation occurs when organisms become separated by a geographical barrier. Over time, distinct species develop due to the separation of the original population.

Sympatric speciation occurs when organisms evolve into distinct species over time in a single location due to specialization and natural selection.

Peripatric speciation is a type of allopatric speciation in which a small part of a population is separated from the main population and evolves in isolation. The founder effect is often observable in the separated population.

Orthopatric is not a type of speciation, so it is the correct answer.

Speciation involves events causing the creation of a new species. Therefore, the separation of the two groups of arabidopsis caused an allopatric speciation event to occur given that the two populations could no longer cross breed. Adaptive radiation involves the rapid diversification of characteristics of a species, which may lead to speciation over time. Artificial speciation involves humans directly influencing allele frequencies. For example, deliberately continuously crossing the largest pigs in a farm to increase the average weight of the pigs. 

Allopatric speciation takes place when a group of individuals becomes physically isolated from the original population and starts to evolve separately. When individuals from the two populations stop mating regularly gene flow is reduced and over time the populations will start to lose the ability to recognize each other and successfully mate. This phenomenon leads to the speciation of one species into two.

Parapatric speciation is a type of speciation that occurs when an extreme change in habitat occurs and separates a species from members of its groups. This does not have to do with geographic barriers, but a difference in climates or conditions. In this case, the salinity of the soil on one side separated the flowers from mating with their own species, thus delineating them.

Allopatric speciation is a separation of species due to geographic location. For example, the speciation of Darwin's finches is allopatric speciation—the finches eventually lost the ability to interbreed due to being on separate islands. 

Sympatric speciation is when a species is still in the same geographic location, but becomes reproductively isolated. This usually happens through a mutation during reproduction when the offspring recieves twice the number of normal chromosomes. This individual possesses a quality called tetraploidy, and cannot reproduce with other diploids. 

Peripatric is similar to allopatric speciation in that the individuals are separated by geographic barriers. However, the main difference is that the group that is broken off is much smaller and may possess a certain quality or trait that, due to the small group, is made a more predominant quality or trait.