Evolutionary logic of colored fruit flesh

Why is fruit flesh fairly pale inside for many fruits (blueberry, apple, grape, etc)?

Perhaps more to the point, is there an evolutionary advantage to fruit having more intensely colored flesh, such as watermelon, raspberry, citrus, kiwi, strawberry?

Animals eat the fruit and distribute the seeds. Brightly coloured fruit is easier to see in between the leaves. Fruit that is easier to see is more likely to be eaten. Also, perhaps a nice red berry looks more appitising to the animal.

Right, but the OP was asking why the flesh of some fruits is colored and that of others isn’t — your explanation only explains why fruits are brightly coloured from the outside.

For melons, at least, a possible answer would be that the plant “wants” animals to eat the flesh (and by extension, the seeds) once the fruit is ripe and the seeds are viable, but not before. So brightly colored flesh and drab exterior would be a natural color scheme for the plants to adopt: melons tend to crack open when they’re good and ripe, exposing the flesh once the seeds are viable but hiding the fruit up to that point.

I didn’t make myself clear. The skin color of fruit has obvious consequences. The flesh, not so much.

Another thing that occurred to me is that some of these, such as kiwi and watermelon, may have been bred by humans seeking a more brilliant red or green - there are yellow-fleshed varieties of both fruits.

Since it’s the outside of the fruit that catches the eye of an animal, there might be nothing driving the selection of the flesh to be bright.

That was exactly my thought. Why, then, the brighter flesh for other fruit?

I’m not sure what the wild ancestor was like, but as others have said the rind splits open when the fruit is ripe, so the bright flesh is a signal to attract animals.

All have flesh that is the same color as the outer part; the pigments just happen to be spread all through the fruit, not just confined to the outside. In wild varieties, the inside would not be more colorful than the outside.

Not sure what the wild ancestor was like, but green is generally not considered to be a prime attractant for fruit-eating animals.

There certainly are some fruits that have distinctly coloured flesh, often of a totally different tone to the skin. So it’s not just the pigment being distributed throughout, the plant is making an ‘effort’ to colour the flesh. The most obvious example is the guava, where even the wild form has pale yellow or green rind with bright pink or orange flesh. (guava fruit: http://www.tropicalfruitnursery.com/images/Guava-lg.jpg). Then there are mangoes where the flesh is bright yellow while the rind is straw coloured or reddish in the wild form.

The reason for this has always seemed pretty obvious to me. Guavas and most of the other fruits with brightly coloured flesh are large fruits, far larger than could be eaten by most birds or even many mammals in one sitting. However many birds and small mammals feed in groups, or at least multiple individuals feed in the same tree serially. By making the half-eaten fruit brightly coloured the fruit is double dipping. It’s able to advertise the presence of ripe fruit with two distinct colours rather than havingto rely on just one.

The colouration also presumably advertises to feeders that the hard work has been done; that the rind has been cracked and that the fruit is indeed ripe. In that way the tree gets the maximum dipsersal from every fruit that is damaged by feeding, rather than risking feeders ‘sampling’ unripe fruit to determine ripeness or starting on undamaged fruit that have a much longer ‘branchlife’. That last point is probably very important for mangoes where the single seed is massive and disperal is almost always by mammals such as monkeys and bats. Rather than having mammals take one bite out of each fruit the tree encourages animals to finish what someone else started and take the fruit away with them to finish rather than leaving it to rot and fall into the shade of the parent.