The number of linkage groups of a particular species corresponds to...

All the genes located on a single chromosome are inherited together and form one linkage group.

Since homologous chromosomes possess identical loci for genes, they constitute the same linkage group.

Therefore, the number of linkage groups in a species is equal to its haploid number of chromosomes (n$).<br><br>For example, in humans (2n = 46$), the haploid number is $23$, so there are $23$ linkage groups. In Drosophila (2n = 8$), the haploid number is 4$, so there are $4$ linkage groups.

Answer: haploid